System for controlling articulation forces

ABSTRACT

In some aspects, a control algorithm is provided for manipulating a pair of articulation arms configured to control an articulation angle of an end effector of a robotic surgical instrument. Other aspects of the present disclosure focus on the robotic arm system, including the pair of articulation arms coupled to the end effector and guided by independent motors controlled by a control circuit. Each of the articulation arms are designed to exert antagonistic forces competing against each other that are apportioned according to a ratio specified in the control algorithm. The ratio of the antagonistic forces may be used to determine the articulation angle of the head or end effector of the robotic surgical arm.

TECHNICAL FIELD

The present disclosure generally relates to robotic surgicalinstruments. In particular, the present disclosures relate to a systemfor controlling articulation forces in a robotic surgical arm with asurgical end effector.

BACKGROUND

Robotic surgical tools may be useful in providing stable and reliableapplication for surgical procedures. Various components may beinterchangeable such that a single support apparatus may be used toattach to different modular robotic surgical arms. Some of these roboticsystems employ multiple motors to control individual components that maymove independently but still involve a degree of interrelationship.

SUMMARY

In one aspect, a system for a robotic surgical instrument is presented.The system may include: a control circuit; a first motor and a secondmotor, both communicatively coupled to the control circuit; a firstarticulation arm communicatively coupled to the first motor; a secondarticulation arm communicatively coupled to the second motor; an endeffector coupled to the first articulation arm via a first hinge and thesecond articulation arm via a second hinge. The control circuit may beconfigured to cause the first motor to apply a first force to the firstarticulation arm. The control circuit may be configured to cause thesecond motor to apply a second force to the second articulation arm,wherein the second force is antagonistic to the first force such thatthe first and second forces apply counteracting forces at the endeffector. The first and second forces may cause the end effector toarticulate via the first and second hinges.

In some aspects, the end effector is configured to articulate to aprescribed angle based on a ratio of magnitudes between the first forceand the second force. In some aspects, the system further includes anarticulation pivot coupled to the end effector, wherein the end effectoris further configured to articulate about the articulation pivot. Insome aspects, the articulation pivot is positioned off of a center axisrunning longitudinally in between and equidistant from at least aportion of the first and second articulation arms.

In another aspect, a method of a robotic surgical instrument comprisinga control circuit, a first motor, a second motor, a first articulationarm, a second articulation arm, and an end effector is presented. Themethod may include: instructing, by the control circuit, the first motorto apply a first force to the first articulation arm; instructing, bythe control circuit, the second motor to apply a second force to thesecond articulation arm, wherein the second force is antagonistic to thefirst force such that the first and second forces apply counteractingforces at the end effector; and causing the end effector to articulatevia first and second hinges based on the first and second forces appliedto the first and second articulation arms, respectively.

FIGURES

FIG. 1 is a perspective view of one robotic controller according to oneaspect of this disclosure.

FIG. 2 is a perspective view of one robotic surgical armcart/manipulator of a robotic surgical system operably supporting aplurality of surgical tool according to one aspect of this disclosure.

FIG. 3 is a side view of the robotic surgical arm cart/manipulatordepicted in FIG. 2 according to one aspect of this disclosure.

FIG. 4 is a perspective view of a surgical tool according to one aspectof this disclosure.

FIG. 5 is an exploded assembly view of an adapter and tool holderarrangement for attaching various surgical tools according to one aspectof this disclosure.

FIG. 6 is a partial bottom perspective view of the surgical tool aspectof FIG. 4 according to one aspect of this disclosure.

FIG. 7 is a partial exploded view of a portion of an articulatablesurgical end effector according to one aspect of this disclosure.

FIG. 8 is a rear perspective view of the surgical tool of FIG. 105 withthe tool mounting housing removed according to one aspect of thisdisclosure.

FIG. 9 is a front perspective view of the surgical tool of FIG. 6 withthe tool mounting housing removed according to one aspect of thisdisclosure.

FIG. 10 is a partial exploded perspective view of the surgical tool ofFIG. 6 according to one aspect of this disclosure.

FIG. 11A is a partial cross-sectional side view of the surgical tool ofFIG. 6 according to one aspect of this disclosure.

FIG. 11B is an enlarged cross-sectional view of a portion of thesurgical tool depicted in FIG. 11A according to one aspect of thisdisclosure.

FIG. 12 illustrates one aspect of an end effector comprising a firstsensor and a second according to one aspect of this disclosure.

FIG. 13A illustrates an aspect wherein the tissue compensator isremovably attached to the anvil portion of the end effector according toone aspect of this disclosure.

FIG. 13B illustrates a detail view of a portion of the tissuecompensator shown in FIG. 13A according to one aspect of thisdisclosure.

FIG. 13C illustrates various example aspects that use the layer ofconductive elements and conductive elements in the staple cartridge todetect the distance between the anvil and the upper surface of thestaple cartridge according to one aspect of this disclosure.

FIG. 14A illustrates an end effector comprising conductors embeddedwithin according to one aspect of this disclosure.

FIG. 14B illustrates an end effector comprising conductors embeddedwithin according to one aspect of this disclosure.

FIG. 15A illustrates a cutaway view of the staple cartridge according toone aspect of this disclosure.

FIG. 15B illustrates a cutaway view of the staple cartridge shown inFIG. 15A illustrating conductors embedded within the end effectoraccording to one aspect of this disclosure.

FIG. 16 illustrates one aspect of a left-right segmented flexiblecircuit for an end effector according to one aspect of this disclosure.

FIG. 17 illustrates one aspect of a segmented flexible circuitconfigured to fixedly attach to a jaw member of an end effectoraccording to one aspect of this disclosure.

FIG. 18 illustrates one aspect of a segmented flexible circuitconfigured to mount to a jaw member of an end effector according to oneaspect of this disclosure.

FIG. 19 illustrates one aspect of an end effector configured to measurea tissue gap GT according to one aspect of this disclosure.

FIG. 20 illustrates one aspect of an end effector comprising segmentedflexible circuit, according to one aspect of this present disclosure.

FIG. 21 illustrates the end effector shown in FIG. 20 with the jawmember clamping tissue between the jaw member and the staple cartridgeaccording to one aspect of this disclosure.

FIG. 22 illustrates a logic diagram of one aspect of a feedback systemaccording to one aspect of this disclosure.

FIG. 23 illustrates a control circuit configured to control aspects ofthe robotic surgical system according to one aspect of this disclosure.

FIG. 24 illustrates a combinational logic circuit configured to controlaspects of the robotic surgical system according to one aspect of thisdisclosure.

FIG. 25 illustrates a sequential logic circuit configured to controlaspects of the robotic surgical system according to one aspect of thisdisclosure.

FIG. 26 illustrates a logic diagram of a common control module for usewith a plurality of motors of the robotic surgical instrument accordingto one aspect of this disclosure.

FIG. 27 is a diagram of an absolute positioning system of the surgicalinstrument of FIG. 1 where the absolute positioning system comprises acontrolled motor drive circuit arrangement comprising a sensorarrangement according to one aspect of this disclosure.

FIG. 28 is a diagram of a position sensor comprising a magnetic rotaryabsolute positioning system according to one aspect of this disclosure.

FIG. 29 is a section view of an end effector of the surgical instrumentof FIG. 1 showing a firing member stroke relative to tissue graspedwithin the end effector according to one aspect of this disclosure.

FIG. 30 is a schematic diagram of a robotic surgical instrumentconfigured to operate the surgical tool described herein according toone aspect of this disclosure.

FIG. 31 shows an example structural portion of a robotic surgical armincluding two articulation arms connected to an end effector, accordingto some aspects of the present disclosure.

FIG. 32 shows the anvil in a neutral or straight position relative tothe articulation arms.

FIG. 33 shows the left articulation arm moved up along a firstdirection, while simultaneously the right articulation arm is moved downalong an opposite direction.

FIG. 34 shows reverse movements by the articulation arms that cause theanvil to move in the reverse, i.e., clockwise, direction.

FIG. 35 shows, according to some aspects, the pivot moment of the endeffector is actually off from the centerline of the shaft structure.

FIG. 36 shows an example graph representing an amount of force appliedby both of the articulation arms as a function of a degree ofarticulation of the head from a horizontal centerline, according to someaspects.

FIG. 37 shows an example of how forces may be applied to the twoarticulation arms in order to cause the head/end effector to articulate60° from the centerline, according to some aspects.

FIG. 38 shows another example of how forces may be applied to the twoarticulation arms in order to cause the head/end effector to articulate30° from the centerline, according to some aspects.

FIG. 39 shows a third example of how forces may be applied to the twoarticulation arms in order to cause the head/end effector to articulateback to the center or neutral position, according to some aspects.

FIG. 40 illustrates a logic flow diagram depicting a process of acontrol program or a logic configuration for causing articulation of anend effector of a robotic surgical system based on controlling twoindependent articulation arms, according to some aspects.

DESCRIPTION

Applicant of the present application owns the following patentapplications filed concurrently herewith and which are each hereinincorporated by reference in their respective entireties:

U.S. patent application Ser. No. 15/636,837, titled CLOSED LOOP VELOCITYCONTROL TECHNIQUES FOR ROBOTIC SURGICAL, by inventors Frederick E.Shelton, IV et al., filed Jun. 29, 2017.

U.S. patent application Ser. No. 15/636,844, titled CLOSED LOOP VELOCITYCONTROL OF CLOSURE MEMBER FOR ROBOTIC SURGICAL INSTRUMENT, by inventorsFrederick E. Shelton, IV et al., filed Jun. 29, 2017.

U.S. patent application Ser. No. 15/636,854, titled ROBOTIC SURGICALINSTRUMENT WITH CLOSED LOOP FEEDBACK TECHNIQUES FOR ADVANCEMENT OFCLOSURE MEMBER DURING FIRING, by inventors Frederick E. Shelton, IV etal., filed Jun. 29, 2017.

U.S. patent application Ser. No. 15/636,829, titled CLOSED LOOP VELOCITYCONTROL TECHNIQUES FOR ROBOTIC SURGICAL INSTRUMENT, by inventorsFrederick E. Shelton, IV et al., filed Jun. 29, 2017.

FIG. 1 depicts one aspect of a master robotic controller 11 that may beused in connection with a robotic arm slave cart 100 of the typedepicted in FIG. 2. The master controller 11 and robotic arm slave cart100, as well as their respective components and control systems arecollectively referred to herein as a robotic surgical system 10.Examples of such systems and devices are disclosed in U.S. Pat. No.7,524,320, which is incorporated herein by reference. The mastercontroller 11 generally includes master controllers (generallyrepresented as 13 in FIG. 1) which are grasped by the surgeon andmanipulated in space while the surgeon views the procedure via a stereodisplay 12. The master controllers 11 generally comprise manual inputdevices which preferably move with multiple degrees of freedom, andwhich often further have an actuatable handle for actuating tools (forexample, for closing grasping saws, applying an electrical potential toan electrode, or the like). Other arrangements may provide the surgeonwith a feed back meter 15 that may be viewed through the display 12 andprovide the surgeon with a visual indication of the amount of forcebeing applied to the cutting instrument or dynamic clamping member.Additional examples are disclosed in U.S. Pat. No. 9,237,891, which isincorporated herein by reference.

As can be seen in FIG. 2, in one form, the robotic arm cart 100 isconfigured to actuate a plurality of surgical tools, generallydesignated as 200. Various robotic surgery systems and methods employingmaster controller and robotic arm cart arrangements are disclosed inU.S. Pat. No. 6,132,368, entitled “Multi-Component Telepresence Systemand Method”, the full disclosure of which is incorporated herein byreference. In various forms, the robotic arm cart 100 includes a base102 from which, in the illustrated aspect, three surgical tools 200 aresupported. In various forms, the surgical tools 200 are each supportedby a series of manually articulatable linkages, generally referred to asset-up joints 104, and a robotic manipulator 106.

Referring now to FIG. 3, in at least one form, robotic manipulators 106may include a linkage 108 that constrains movement of the surgical tool200. In various aspects, linkage 108 includes rigid links coupledtogether by rotational joints in a parallelogram arrangement so that thesurgical tool 200 rotates around a point in space 110, as more fullydescribed in issued U.S. Pat. No. 5,817,084, the full disclosure ofwhich is herein incorporated by reference. The parallelogram arrangementconstrains rotation to pivoting about an axis 112 a, sometimes calledthe pitch axis. The links supporting the parallelogram linkage arepivotally mounted to set-up joints 104 (FIG. 2) so that the surgicaltool 200 further rotates about an axis 112 b, sometimes called the yawaxis. The pitch and yaw axes 112 a, 112 b intersect at the remote center114, which is aligned along a shaft 208 of the surgical tool 200. Thesurgical tool 200 may have further degrees of driven freedom assupported by manipulator 106, including sliding motion of the surgicaltool 200 along the longitudinal tool axis “LT-LT”. As the surgical tool200 slides along the tool axis LT-LT relative to manipulator 106 (arrow112 c), remote center 114 remains fixed relative to base 116 ofmanipulator 106. Hence, the entire manipulator is generally moved tore-position remote center 114. Linkage 108 of manipulator 106 is drivenby a series of motors 120. These motors actively move linkage 108 inresponse to commands from a processor of a control system. As will bediscussed in further detail below, motors 120 are also employed tomanipulate the surgical tool 200.

FIG. 4 is a perspective view of a surgical tool 200 that is adapted foruse with a robotic surgical system 10 that has a tool drive assemblythat is operatively coupled to a master controller 11 that is operableby inputs from an operator (i.e., a surgeon) is depicted in FIG. 4. Ascan be seen in that Figure, the surgical tool 200 includes a surgicalend effector 1012 that comprises an endocutter. In at least one form,the surgical tool 200 generally includes an elongated shaft assembly1008 that has a proximal closure tube 1040 and a distal closure tube1042 that are coupled together by an articulation joint 1011. Thesurgical tool 200 is operably coupled to the manipulator by a toolmounting portion, generally designated as 300. The surgical tool 200further includes an interface 230 which mechanically and electricallycouples the tool mounting portion 300 to the manipulator. In variousaspects, the tool mounting portion 300 includes a tool mounting plate302 that operably supports a plurality of (four are shown in FIG. 6)rotatable body portions, driven discs or elements 304, that each includea pair of pins 306 that extend from a surface of the driven element 304.One pin 306 is closer to an axis of rotation of each driven elements 304than the other pin 306 on the same driven element 304, which helps toensure positive angular alignment of the driven element 304. Interface230 includes an adaptor portion 240 that is configured to mountinglyengage the mounting plate 302 as will be further discussed below. Theadaptor portion 240 may include an array of electrical connecting pinswhich may be coupled to a memory structure by a circuit board within thetool mounting portion 300. While interface 230 is described herein withreference to mechanical, electrical, and magnetic coupling elements, itshould be understood that a wide variety of telemetry modalities mightbe used, including infrared, inductive coupling, or the like.

FIG. 5 is an exploded assembly view of an adapter and tool holderarrangement for attaching various surgical tools according to one aspectof this disclosure. A detachable latch arrangement 239 may be employedto releasably affix the adaptor 240 to the tool holder 270. As usedherein, the term “tool drive assembly” when used in the context of therobotic surgical system 10, at least encompasses various aspects of theadapter 240 and tool holder 270 and which has been generally designatedas 101 in FIG. 5. For example, as can be seen in FIG. 5, the tool holder270 may include a first latch pin arrangement 274 that is sized to bereceived in corresponding clevis slots 241 provided in the adaptor 240.In addition, the tool holder 270 may further have second latch pins 276that are sized to be retained in corresponding latch devises in theadaptor 240. In at least one form, a latch assembly 245 is movablysupported on the adapter 240 and is biasable between a first latchedposition wherein the latch pins 276 are retained within their respectivelatch clevis and an unlatched position wherein the second latch pins 276may be into or removed from the latch devises. A spring or springs (notshown) are employed to bias the latch assembly into the latchedposition. A lip on the tool side 244 of adaptor 240 may slidably receivelaterally extending tabs of tool mounting housing 301. The adaptorportion 240 may include an array of electrical connecting pins 242 whichmay be coupled to a memory structure by a circuit board within the toolmounting portion 300. While interface 230 is described herein withreference to mechanical, electrical, and magnetic coupling elements, itshould be understood that a wide variety of telemetry modalities mightbe used, including infrared, inductive coupling, or the like.

As shown in FIGS. 4-6 the adapter portion 240 generally includes a toolside 244 and a holder side 246. In various forms, a plurality ofrotatable bodies 250 are mounted to a floating plate 248 which has alimited range of movement relative to the surrounding adaptor structurenormal to the major surfaces of the adaptor 240. Axial movement of thefloating plate 248 helps decouple the rotatable bodies 250 from the toolmounting portion 300 when the levers 303 along the sides of the toolmounting portion housing 301 are actuated. Other mechanisms/arrangementsmay be employed for releasably coupling the tool mounting portion 300 tothe adaptor 240. In at least one form, rotatable bodies 250 areresiliently mounted to floating plate 248 by resilient radial memberswhich extend into a circumferential indentation about the rotatablebodies 250. The rotatable bodies 250 can move axially relative to plate248 by deflection of these resilient structures. When disposed in afirst axial position (toward tool side 244) the rotatable bodies 250 arefree to rotate without angular limitation. However, as the rotatablebodies 250 move axially toward tool side 244, tabs 252 (extendingradially from the rotatable bodies 250) laterally engage detents on thefloating plates so as to limit angular rotation of the rotatable bodies250 about their axes. This limited rotation can be used to helpdrivingly engage the rotatable bodies 250 with drive pins 272 of acorresponding tool holder portion 270 of the robotic system 10, as thedrive pins 272 will push the rotatable bodies 250 into the limitedrotation position until the pins 11234 are aligned with (and slide into)openings 256′. Openings 256 on the tool side 244 and openings 256′ onthe holder side 246 of rotatable bodies 250 are configured to accuratelyalign the driven elements 304 of the tool mounting portion 300 with thedrive elements 271 of the tool holder 270. As described above regardinginner and outer pins 306 of driven elements 304, the openings 256, 256′are at differing distances from the axis of rotation on their respectiverotatable bodies 250 so as to ensure that the alignment is not 180degrees from its intended position. Additionally, each of the openings256 is slightly radially elongated so as to fittingly receive the pins306 in the circumferential orientation. This allows the pins 306 toslide radially within the openings 256, 256′ and accommodate some axialmisalignment between the tool 200 and tool holder 270, while minimizingany angular misalignment and backlash between the drive and drivenelements. Openings 256 on the tool side 244 are offset by about 90degrees from the openings 256′ (shown in broken lines) on the holderside 246.

FIG. 6 is a partial bottom perspective view of the surgical tool aspectof FIG. 4. As shown in FIGS. 6-10, the surgical end effector 1012 isattached to the tool mounting portion 300 by an elongated shaft assembly1008 according to various aspects. As shown in the illustrated aspect,the shaft assembly 1008 includes an articulation joint generallyindicated as 1011 that enables the surgical end effector 1012 to beselectively articulated about an articulation axis AA-AA that issubstantially transverse to a longitudinal tool axis LT-LT. See FIG. 7.In other aspects, the articulation joint is omitted. In various aspects,the shaft assembly 1008 may include a closure tube assembly 1009 thatcomprises a proximal closure tube 1040 and a distal closure tube 1042that are pivotably linked by a pivot links 1044 and operably supportedon a spine assembly generally depicted as 1049. In the illustratedaspect, the spine assembly 1049 comprises a distal spine portion 1050that is attached to the elongated channel 1022 and is pivotally coupledto the proximal spine portion 1052. The closure tube assembly 1009 isconfigured to axially slide on the spine assembly 1049 in response toactuation motions applied thereto. The distal closure tube 1042 includesan opening 1045 into which the tab 1027 on the anvil 1024 is inserted inorder to facilitate opening of the anvil 1024 as the distal closure tube1042 is moved axially in the proximal direction “PD”. The closure tubes1040, 1042 may be made of electrically conductive material (such asmetal) so that they may serve as part of the antenna, as describedabove. Components of the main drive shaft assembly (e.g., the driveshafts 1048, 1050) may be made of a nonconductive material (such asplastic). The anvil 1024 may be pivotably opened and closed at a pivotpoint 1025 located at the proximal end of the elongated channel 1022.

In use, it may be desirable to rotate the surgical end effector 1012about the longitudinal tool axis LT-LT. In at least one aspect, the toolmounting portion 300 includes a rotational transmission assembly 1069that is configured to receive a corresponding rotary output motion fromthe tool drive assembly 101 of the robotic surgical system 10 andconvert that rotary output motion to a rotary control motion forrotating the elongated shaft assembly 1008 (and surgical end effector1012) about the longitudinal tool axis LT-LT. In various aspects, forexample, the proximal end 1060 of the proximal closure tube 1040 isrotatably supported on the tool mounting plate 302 of the tool mountingportion 300 by a forward support cradle 309 and a closure sled 1100 thatis also movably supported on the tool mounting plate 302. In at leastone form, the rotational transmission assembly 1069 includes a tube gearsegment 1062 that is formed on (or attached to) the proximal end 1060 ofthe proximal closure tube 1040 for operable engagement by a rotationalgear assembly 1070 that is operably supported on the tool mounting plate302. As shown in FIG. 8, the rotational gear assembly 1070, in at leastone aspect, comprises a rotation drive gear 1072 that is coupled to acorresponding first one of the driven discs or elements 304 on theadapter side 307 of the tool mounting plate 302 when the tool mountingportion 300 is coupled to the tool drive assembly 101. See FIG. 6. Therotational gear assembly 1070 further comprises a rotary driven gear1074 that is rotatably supported on the tool mounting plate 302 inmeshing engagement with the tube gear segment 1062 and the rotationdrive gear 1072. Application of a first rotary output motion from thetool drive assembly 101 of the robotic surgical system 10 to thecorresponding driven element 304 will thereby cause rotation of therotation drive gear 1072. Rotation of the rotation drive gear 1072ultimately results in the rotation of the elongated shaft assembly 1008(and the surgical end effector 1012) about the longitudinal tool axisLT-LT (represented by arrow “R” in FIG. 8). It will be appreciated thatthe application of a rotary output motion from the tool drive assembly101 in one direction will result in the rotation of the elongated shaftassembly 1008 and surgical end effector 1012 about the longitudinal toolaxis LT-LT in a first direction and an application of the rotary outputmotion in an opposite direction will result in the rotation of theelongated shaft assembly 1008 and surgical end effector 1012 in a seconddirection that is opposite to the first direction.

In at least one aspect, the closure of the anvil 1024 relative to thestaple cartridge 1034 is accomplished by axially moving the closure tubeassembly 1009 in the distal direction “DD” on the spine assembly 1049.As indicated above, in various aspects, the proximal end 1060 of theproximal closure tube 1040 is supported by the closure sled 1100 whichcomprises a portion of a closure transmission, generally depicted as1099. In at least one form, the closure sled 1100 is configured tosupport the closure tube 1009 on the tool mounting plate 320 such thatthe proximal closure tube 1040 can rotate relative to the closure sled1100, yet travel axially with the closure sled 1100. In particular, theclosure sled 1100 has an upstanding tab 1101 that extends into a radialgroove 1063 in the proximal end portion of the proximal closure tube1040. In addition, as can be seen in FIG. 10, the closure sled 1100 hasa tab portion 1102 that extends through a slot 305 in the tool mountingplate 302. The tab portion 1102 is configured to retain the closure sled1100 in sliding engagement with the tool mounting plate 302. In variousaspects, the closure sled 1100 has an upstanding portion 1104 that has aclosure rack gear 1106 formed thereon. The closure rack gear 1106 isconfigured for driving engagement with a closure gear assembly 1110. Theknife rack gear 1106 is slidably supported within a rack housing 1210that is attached to the tool mounting plate 302 such that the knife rackgear 1106 is retained in meshing engagement with a knife gear assembly1220.

In various forms, the closure gear assembly 1110 includes a closure spurgear 1112 that is coupled to a corresponding second one of the drivendiscs or elements 304 on the adapter side 307 of the tool mounting plate302. See FIG. 6. Thus, application of a second rotary output motion fromthe tool drive assembly 101 of the robotic surgical system 10 to thecorresponding second driven element 304 will cause rotation of theclosure spur gear 1112 when the tool mounting portion 300 is coupled tothe tool drive assembly 101. The closure gear assembly 1110 furtherincludes a closure reduction gear set 1114 that is supported in meshingengagement with the closure spur gear 1112. As can be seen in FIGS. 9and 10, the closure reduction gear set 1114 includes a driven gear 1116that is rotatably supported in meshing engagement with the closure spurgear 1112. The closure reduction gear set 1114 further includes a firstclosure drive gear 1118 that is in meshing engagement with a secondclosure drive gear 1120 that is rotatably supported on the tool mountingplate 302 in meshing engagement with the closure rack gear 1106. Thus,application of a second rotary output motion from the tool driveassembly 101 of the robotic surgical system 10 to the correspondingsecond driven element 11304 will cause rotation of the closure spur gear1112 and the closure transmission 1110 and ultimately drive the closuresled 1100 and closure tube assembly 1009 axially. The axial direction inwhich the closure tube assembly 1009 moves ultimately depends upon thedirection in which the second driven element 304 is rotated. Forexample, in response to one rotary output motion received from the tooldrive assembly 101 of the robotic surgical system 10, the closure sled1100 will be driven in the distal direction “DD” and ultimately drivethe closure tube assembly 101 in the distal direction. As the distalclosure tube 1042 is driven distally, the end of the closure tubesegment 1042 will engage a portion of the anvil 1024 and cause the anvil1024 to pivot to a closed position. Upon application of an “opening” output motion from the tool drive assembly 101 of the robotic surgicalsystem 10, the closure sled 1100 and shaft assembly 1008 will be drivenin the proximal direction “PD”. As the distal closure tube 1042 isdriven in the proximal direction, the opening 1045 therein interactswith the tab 1027 on the anvil 1024 to facilitate the opening thereof.In various aspects, a spring (not shown) may be employed to bias theanvil to the open position when the distal closure tube 1042 has beenmoved to its starting position. In various aspects, the various gears ofthe closure gear assembly 1110 are sized to generate the necessaryclosure forces needed to satisfactorily close the anvil 1024 onto thetissue to be cut and stapled by the surgical end effector 1012. Forexample, the gears of the closure transmission 1110 may be sized togenerate approximately 70-120 pounds.

FIG. 11A is a partial cross-sectional side view of the surgical tool 200of FIG. 6 and FIG. 11B is an enlarged cross-sectional view of a portionof the surgical tool depicted in FIG. 11A according to one aspect ofthis disclosure. With reference to FIGS. 11A and 11B, the distal end1202 of the knife bar 1200 is attached to the cutting instrument 1032.The proximal end 1204 of the knife bar 1200 is rotatably affixed to aknife rack gear 1206 such that the knife bar 1200 is free to rotaterelative to the knife rack gear 1206. The knife rack gear 1206 isslidably supported within a rack housing 1210 that is attached to thetool mounting plate 302 such that the knife rack gear 1206 is retainedin meshing engagement with a knife gear assembly 1220. More specificallyand with reference to FIG. 10, in at least one aspect, the knife gearassembly 1220 includes a knife spur gear 1222 that is coupled to acorresponding third one of the driven discs or elements 304 on theadapter side 307 of the tool mounting plate 302. See FIG. 6. Thus,application of another rotary output motion from the robotic system 10through the tool drive assembly 101 to the corresponding third drivenelement 304 will cause rotation of the knife spur gear 1222. The knifegear assembly 1220 further includes a knife gear reduction set 1224 thatincludes a first knife drive gear 1226 and a second knife drive gear1228. The knife gear reduction set 1224 is rotatably mounted to the toolmounting plate 302 such that the first knife drive gear 1226 is inmeshing engagement with the knife spur gear 1222. Likewise, the secondknife drive gear 1228 is in meshing engagement with a third knife drivegear 1230 that is rotatably supported on the tool mounting plate 302 inmeshing engagement with the knife rack gear 1206. In various aspects,the gears of the knife gear assembly 1220 are sized to generate theforces needed to drive the cutting element 1032 through the tissueclamped in the surgical end effector 1012 and actuate the staplestherein. For example, the gears of the knife drive assembly 1230 may besized to generate approximately 40 to 100 pounds. It will be appreciatedthat the application of a rotary output motion from the tool driveassembly 101 in one direction will result in the axial movement of thecutting instrument 1032 in a distal direction and application of therotary output motion in an opposite direction will result in the axialtravel of the cutting instrument 1032 in a proximal direction.

In various aspects, the surgical tool 200 employs an articulation systemthat includes an articulation joint 12011 that enables the surgical endeffector 1012 to be articulated about an articulation axis AA-AA that issubstantially transverse to the longitudinal tool axis LT-LT. In atleast one aspect, the surgical tool 200 includes first and secondarticulation bars 1250 a, 1250 b that are slidably supported withincorresponding passages provided through the proximal spine portion 1052.In at least one form, the first and second articulation bars 1250 a,1250 b are actuated by an articulation transmission that is operablysupported on the tool mounting plate 302. Each of the articulation bars1250 a, 1250 b has a proximal end that has a guide rod protrudingtherefrom which extend laterally through a corresponding slot in theproximal end portion of the proximal spine portion and into acorresponding arcuate slot in an articulation nut 1260 which comprises aportion of the articulation transmission. The articulation bar 1250 ahas a guide rod 1254 which extends laterally through a correspondingslot in the proximal end portion of the distal spine portion 1050 andinto a corresponding arcuate slot in the articulation nut 1260. Inaddition, the articulation bar 1250 a has a distal end that is pivotallycoupled to the distal spine portion 1050 by, for example, a pin andarticulation bar 1250 b has a distal end that is pivotally coupled tothe distal spine portion 1050 by a pin. In particular, the articulationbar 1250 a is laterally offset in a first lateral direction from thelongitudinal tool axis LT-LT and the articulation bar 1250 b islaterally offset in a second lateral direction from the longitudinaltool axis LT-LT. Thus, axial movement of the articulation bars 1250 a,1250 b in opposing directions will result in the articulation of thedistal spine portion 1050 as well as the surgical end effector 1012attached thereto about the articulation axis AA-AA as will be discussedin further detail below.

Articulation of the surgical end effector 1012 is controlled by rotatingthe articulation nut 1260 about the longitudinal tool axis LT-LT. Thearticulation nut 1260 is rotatably journaled on the proximal end portionof the distal spine portion 1050 and is rotatably driven thereon by anarticulation gear assembly 1270. More specifically and with reference toFIG. 8, in at least one aspect, the articulation gear assembly 1270includes an articulation spur gear 1272 that is coupled to acorresponding fourth one of the driven discs or elements 304 on theadapter side 307 of the tool mounting plate 302. Thus, application ofanother rotary input motion from the robotic system 10 through the tooldrive assembly 101 to the corresponding fourth driven element 304 willcause rotation of the articulation spur gear 1272 when the interface 230is coupled to the tool holder 270. An articulation drive gear 1274 isrotatably supported on the tool mounting plate 302 in meshing engagementwith the articulation spur gear 1272 and a gear portion 1264 of thearticulation nut 1260 as shown. The articulation nut 1260 has a shoulder1266 formed thereon that defines an annular groove 1267 for receivingretaining posts 1268 therein. Retaining posts 1268 are attached to thetool mounting plate 302 and serve to prevent the articulation nut 1260from moving axially on the proximal spine portion 1052 while maintainingthe ability to be rotated relative thereto. Thus, rotation of thearticulation nut 1260 in a first direction, will result in the axialmovement of the articulation bar 1250 a in a distal direction “DD” andthe axial movement of the articulation bar 1250 b in a proximaldirection “PD” because of the interaction of the guide rods 1254 withthe spiral slots in the articulation gear 1260. Similarly, rotation ofthe articulation nut 1260 in a second direction that is opposite to thefirst direction will result in the axial movement of the articulationbar 1250 a in the proximal direction “PD” as well as cause articulationbar 1250 b to axially move in the distal direction “DD”. Thus, thesurgical end effector 1012 may be selectively articulated aboutarticulation axis “AA-AA” in a first direction “FD” by simultaneouslymoving the articulation bar 1250 a in the distal direction “DD” and thearticulation bar 1250 b in the proximal direction “PD”. Likewise, thesurgical end effector 1012 may be selectively articulated about thearticulation axis “AA-AA” in a second direction “SD” by simultaneouslymoving the articulation bar 1250 a in the proximal direction “PD” andthe articulation bar 1250 b in the distal direction “DD.”

The tool aspect described above employs an interface arrangement that isparticularly well-suited for mounting the robotically controllablemedical tool onto at least one form of robotic arm arrangement thatgenerates at least four different rotary control motions. Those ofordinary skill in the art will appreciate that such rotary outputmotions may be selectively controlled through the programmable controlsystems employed by the robotic system/controller. For example, the toolarrangement described above may be well-suited for use with thoserobotic systems manufactured by Intuitive Surgical, Inc. of Sunnyvale,Calif., U.S.A., many of which may be described in detail in variouspatents incorporated herein by reference. The unique and novel aspectsof various aspects of the present invention serve to utilize the rotaryoutput motions supplied by the robotic system to generate specificcontrol motions having sufficient magnitudes that enable end effectorsto cut and staple tissue. Thus, the unique arrangements and principlesof various aspects of the present invention may enable a variety ofdifferent forms of the tool systems disclosed and claimed herein to beeffectively employed in connection with other types and forms of roboticsystems that supply programmed rotary or other output motions. Inaddition, as will become further apparent as the present DetailedDescription proceeds, various end effector aspects of the presentinvention that require other forms of actuation motions may also beeffectively actuated utilizing one or more of the control motionsgenerated by the robotic system.

FIG. 12 illustrates one aspect of an end effector 3000 comprising afirst sensor 3008 a and a second sensor 3008 b. The first and secondsensors 3008 a, 3008 b are provided on the cartridge deck to determinetissue location using segmented electrodes. Accordingly, the first andsecond sensors 3008 a, 3008 b enable sensing the load on the closuretube, the position of the closure tube, the firing member at the rackand the position of the firing member coupled to the I-beam 3005, theportion of the cartridge that contains tissue, the load and position onthe articulation rods. The end effector 3000 comprises a first jawmember, or anvil, 3002 pivotally coupled to a second jaw member 3004.The second jaw member 3004 is configured to receive a staple cartridge3006 therein. The staple cartridge 3006 comprises a plurality ofstaples. The plurality of staples is deployable from the staplecartridge 3006 during a surgical operation. The end effector 3000comprises a first sensor 3008 a. The first sensor 3008 a is configuredto measure one or more parameters of the end effector 3000. For example,in one aspect, the first sensor 3008 a is configured to measure the gap3010 between the anvil 3002 and the second jaw member 3004. The firstsensor 3008 a may comprise, for example, a Hall effect sensor configuredto detect a magnetic field generated by a magnet 3012 embedded in thesecond jaw member 3004 and/or the staple cartridge 3006. As anotherexample, in one aspect, the first sensor 3008 a is configured to measureone or more forces exerted on the anvil 3002 by the second jaw member3004 and/or tissue clamped between the anvil 3002 and the second jawmember 3004. The sensors 3008 a, 3008 b may be employed to measuretissue thickness, force, displacement, compression, tissue impedance,and tissue location within the end effector 3000.

The end effector 3000 comprises a second sensor 3008 b. The secondsensor 3008 b is configured to measure one or more parameters of the endeffector 3000. For example, in various aspects, the second sensor 3008 bmay comprise a strain gauge configured to measure the magnitude of thestrain in the anvil 3002 during a clamped condition. The strain gaugeprovides an electrical signal whose amplitude varies with the magnitudeof the strain. In various aspects, the first sensor 3008 a and/or thesecond sensor 3008 b may comprise, for example, a magnetic sensor suchas, for example, a Hall effect sensor, a strain gauge, a pressuresensor, a force sensor, an inductive sensor such as, for example, aneddy current sensor, a resistive sensor, a capacitive sensor, an opticalsensor, and/or any other suitable sensor for measuring one or moreparameters of the end effector 3000. The first sensor 3008 a and thesecond sensor 3008 b may be arranged in a series configuration and/or aparallel configuration. In a series configuration, the second sensor3008 b may be configured to directly affect the output of the firstsensor 3008 a. In a parallel configuration, the second sensor 3008 b maybe configured to indirectly affect the output of the first sensor 3008a.

In one aspect, the first sensor 3008 a may be configured to measure thegap 3010 between the anvil 3002 and the second jaw member 3004. The gap3010 is representative of the thickness and/or compressibility of atissue section clamped between the anvil 3002 and the staple cartridge3006. The first sensor 3008 a may comprise, for example, a Hall effectsensor configured to detect a magnetic field generated by a magnet 3012coupled to the second jaw member 3004 and/or the staple cartridge 3006.Measuring at a single location accurately describes the compressedtissue thickness for a calibrated full bit of tissue, but may provideinaccurate results when a partial bite of tissue is placed between theanvil 3002 and the second jaw member 3004. A partial bite of tissue,either a proximal partial bite or a distal partial bite, changes theclamping geometry of the anvil 3002.

In some aspects, the second sensor 3008 b may be configured to detectone or more parameters indicative of a type of tissue bite, for example,a full bite, a partial proximal bite, and/or a partial distal bite. Insome aspects, the thickness measurement of the first sensor 3008 a maybe provided to an output device of the robotic surgical system 10coupled to the end effector 3000. For example, in one aspect, the endeffector 3000 is coupled to the robotic surgical system 10 comprising adisplay. The measurement of the first sensor 3008 a is provided to aprocessor.

In another aspect, the end effector 3000 may comprise a plurality ofsecond sensors configured to measure an amplitude of strain exerted onthe anvil 3002 during a clamping procedure. In another aspect, theplurality of sensors allows a robust tissue thickness sensing process tobe implemented. By detecting various parameters along the length of theanvil 3202, the plurality of sensors allow a surgical instrument, suchas, for example, the surgical instrument 10, to calculate the tissuethickness in the jaws regardless of the bite, for example, a partial orfull bite. In some aspects, the plurality of sensors comprises aplurality of strain gauges. The plurality of strain gauges is configuredto measure the strain at various points on the anvil 3002. The amplitudeand/or the slope of the strain at each of the various points on theanvil 3002 can be used to determine the thickness of tissue in betweenthe anvil 3002 and the staple cartridge 3006. The plurality of straingauges may be configured to optimize maximum amplitude and/or slopedifferences based on clamping dynamics to determine thickness, tissueplacement, and/or material properties of the tissue. Time basedmonitoring of the plurality of sensors during clamping allows aprocessor, such as, for example, a primary processor, to utilizealgorithms and look-up tables to recognize tissue characteristics andclamping positions and dynamically adjust the end effector 3000 and/ortissue clamped between the anvil 3002 and the staple cartridge 3006.

FIG. 13A illustrates an aspect of an end effector 5500 comprising alayer of conductive elements 5512. The end effector 5500 is similar tothe end effector 3000 described above. The end effector 5500 comprises afirst jaw member, or anvil, 5502 pivotally coupled to a second jawmember 5504. The second jaw member 5504 is configured to receive astaple cartridge 5506 therein. FIG. 13B illustrates a detail view of aportion of the tissue compensator shown in FIG. 13A. The conductiveelements 5512 can comprise any combination of conductive materials inany number of configurations, such as for instance coils of wire, a meshor grid of wires, conductive strips, conductive plates, electricalcircuits, microprocessors, or any combination thereof. The layercontaining conductive elements 5512 can be located on the anvil-facingsurface 5514 of the tissue compensator 5510. Alternatively oradditionally, the layer of conductive elements 5512 can be located onthe staple cartridge-facing surface 5516 of the tissue compensator 5510.The conductive elements 5512 may be employed to measure tissuethickness, force, displacement, compression, tissue impedance, andtissue location within the end effector 5500. Additional examples aredisclosed in Patent Application No. US 2016/0066912, which isincorporated herein by reference.

FIG. 13C illustrates various example aspects that use the layer ofconductive elements 5512 and conductive elements 5524, 5526, and 5528 inthe staple cartridge 5506 to detect the distance between the anvil 5502and the upper surface of the staple cartridge 5506. The distance betweenthe anvil 5502 and the staple cartridge 5506 indicates the amount and/ordensity of tissue 5518 compressed therebetween. This distance canadditionally or alternatively indicate which areas of the end effector5500 contain tissue. The tissue 5518 thickness, density, and/or locationcan be communicated to the operator of the surgical instrument 10.

In the illustrated example aspects, the layer of conductive elements5512 is located on the anvil-facing surface 5514 of the tissuecompensator 5510, and comprises one or more coils of wire 5522 incommunication with a control circuit comprising a microprocessor 5520.The microprocessor 5500 can be located in the end effector 5500 or anycomponent thereof, or can be located in the tool mounting housing 301 ofthe instrument, or can comprise any microprocessor or microcontrollerpreviously described. In the illustrated example aspects, the staplecartridge 5506 also includes conductive elements, which can be any oneof: one or more coils of wire 5524, one or more conductive plates 5526,a mesh of wires 5528, or any other convenient configuration, or anycombination thereof. The conductive elements of the staple cartridge5506 can be in communication with the same microprocessor 5520 or someother microprocessor in the robotic surgical instrument. The conductiveelements 5512 may be employed to measure tissue thickness, force,displacement, compression, tissue impedance, and tissue location withinthe end effector 5500.

When the anvil 5502 is in a closed position and thus is compressingtissue 5518 against staple cartridge 5506, the layer of conductiveelements 5512 of the tissue compensator 5510 can capacitively couplewith the conductors in staple cartridge 5506. The strength of thecapacitive field between the layer of conductive elements 5512 and theconductive elements of the staple cartridge 5506 can be used todetermine the amount of tissue 5518 being compressed. Alternatively, thestaple cartridge 5506 can comprise eddy current sensors in communicationwith a microprocessor 5520, wherein the eddy current sensors areoperable to sense the distance between the anvil 5502 and the uppersurface of the staple cartridge 5506 using eddy currents.

It is understood that other configurations of conductive elements arepossible, and that the aspects of FIG. 13C are by way of example only,and not limitation. For example, in some aspects the layer of conductiveelements 5512 can be located on the staple cartridge-facing surface 5516of the tissue compensator 5510. Also, in some aspects the conductiveelements 5524, 5526, and/or 5528 can be located on or within the anvil5502. Thus in some aspects, the layer of conductive elements 5512 cancapacitively couple with conductive elements in the anvil 5502 andthereby sense properties of tissue 5518 enclosed within the endeffector.

It can also be recognized that a layer of conductive elements 5512 maybe disposed on both the anvil-facing surface 5514 and thecartridge-facing surface 5516. A system to detect the amount, density,and/or location of tissue 5518 compressed by the anvil 5502 against thestaple cartridge 5506 can comprise conductors or sensors either in theanvil 5502, the staple cartridge 5506, or both. Aspects that includeconductors or sensors in both the anvil 5502 and the staple cartridge5506 can optionally achieve enhanced results by allowing differentialanalysis of the signals that can be achieved by this configuration.

Turning now to FIG. 14A, there is illustrated a close-up cutaway view ofthe end effector 5600 with the anvil 5602 in a closed position. FIG. 14Billustrates the end effector 5600 comprising electrical conductors 5620embedded within according to one aspect of this disclosure. In a closedposition, the anvil 5602 can compress tissue 5618 between the tissuecompensator 5610 and the staple cartridge 5606. In some cases, only apart of the end effector 5600 may be enclosing the tissue 5618. In areasof the end effector 5600 that are enclosing tissue 5618, in areas ofgreater compression 5624, the array of conductors 5620 will also becompressed, while in uncompressed 5626 areas, the array of conductors5620 will be further apart. Hence, the conductivity, resistance,capacitance, and/or some other electrical property between the array ofconductors 5620 can indicate which areas of the end effector 5600contain tissue. The array of conductors 5620 may be employed to measuretissue thickness, force, displacement, compression, tissue impedance,and tissue location within the end effector 5600.

With reference to FIGS. 14A and 14B, the end effector 5600 comprising atissue compensator 5610 further comprising conductors 5620 embeddedwithin. The end effector 5600 comprises a first jaw member, or anvil5602 pivotally coupled to a second jaw member 5604. The second jawmember 5604 is configured to receive a staple cartridge 5606 therein. Insome aspects, the end effector 5600 further comprises a tissuecompensator 5610 removably positioned on the anvil 5602 or the staplecartridge 5606.

An array of conductors 5620 are embedded within the material thatcomprises the tissue compensator 5610. The array of conductors 5620 canbe arranged in an opposing configuration, and the opposing elements canbe separated by insulating material. The array of conductors 5620 areeach coupled to one or more conductive wires 5622. The conductive wires5622 allow the array of conductors 5620 to communicate with amicroprocessor or control circuit 961 (FIG. 22), 800 (FIG. 23), 810(FIG. 24), 820 (FIG. 25), 4420 (FIG. 26), 2510 (FIG. 30). The array ofconductors 5620 may span the width of the tissue compensator 5610 suchthat they will be in the path of a cutting member or knife bar 280. Asthe knife bar 280 advances, it will sever, destroy, or otherwise disablethe conductors 5620, and thereby indicate its position within the endeffector 5600. The array of conductors 5610 can comprise conductiveelements, electric circuits, microprocessors, or any combinationthereof.

FIGS. 15A and 15B illustrate an aspect of an end effector 5650 furthercomprising conductors 5662 embedded therein. The end effector 5650comprises a first jaw member, or anvil, 5652 pivotally coupled to asecond jaw member 5654. The second jaw member 5654 is configured toreceive a staple cartridge 5656 therein. FIG. 15A illustrates a cutawayview of the staple cartridge 5656. The cutaway view illustratesconductors 5670 embedded within the end effector. Each of the conductors5672 is coupled to a conductive wire 5672. The conductive wires 5672allow the array of conductors 5672 to communicate with a microprocessor.The conductors 5672 may comprise conductive elements, electric circuits,microprocessors, or any combination thereof. FIG. 15B illustrates aclose-up side view of the end effector 5650 with the anvil 5652 in aclosed position. In a closed position, the anvil 5652 can compresstissue 5658 against the staple cartridge 5656. The conductors 5672embedded within the tissue compensator 5660 can be operable to applypulses of electrical current 5674, at predetermined frequencies, to thetissue 5658. The same or additional conductors 5672 can detect theresponse of the tissue 5658 and transmit this response to amicroprocessor or microcontroller located in the instrument. Theresponse of the tissue 5658 to the electrical pulses 5674 can be used todetermine a property of the tissue 5658. For example, the galvanicresponse of the tissue 5658 indicates the moisture content in the tissue5658. As another example, measurement of the electrical impedancethrough the tissue 5658 could be used to determine the conductivity ofthe tissue 5648, which is an indicator of the tissue type. Otherproperties that can be determined include by way of example and notlimitation: oxygen content, salinity, density, and/or the presence ofcertain chemicals. By combining data from several sensors, otherproperties could be determined, such as blood flow, blood type, thepresence of antibodies, etc. The conductors 5662 may be employed tomeasure tissue thickness, force, displacement, compression, tissueimpedance, and tissue location within the end effector 5650.

FIG. 16 illustrates one aspect of a left-right segmented flexiblecircuit 4600. The left-right segmented flexible circuit 4600 comprises aplurality of segments L1-L5 on the left side of the left-right segmentedflexible circuit 4600 and a plurality of segments R1-R5 on the rightside of the left-right segmented flexible circuit 4600. Each of thesegments L1-L5 and R1-R5 comprise temperature sensors and/or forcesensors to sense tissue parameters locally within each segment L1-L5 andR1-R5. The left-right segmented flexible circuit 4600 is configured tosense tissue parameters locally within each of the segments L1-L5 andR1-R5. The flexible circuit 4600 may be employed to measure tissuethickness, force, displacement, compression, tissue impedance, andtissue location within an end effector.

FIG. 17 illustrates one aspect of a segmented flexible circuit 6430configured to fixedly attach to a jaw member 6434 of an end effector.The segmented flexible circuit 6430 comprises a distal segment 6432 aand lateral segments 6432 b, 6432 c that include individuallyaddressable sensors to provide local tissue presence detection. Thesegments 6432 a, 6432 b, 6432 c are individually addressable to detecttissue and to measure tissue parameters based on individual sensorslocated within each of the segments 6432 a, 6432 b, 6432 c. The segments6432 a, 6432 b, 6432 c of the segmented flexible circuit 6430 aremounted to the jaw member 6434 and are electrically coupled to an energysource such as an electrical circuit via electrical conductive elements6436. A Hall effect sensor 6438, or any suitable magnetic sensor, islocated on a distal end of the jaw member 6434. The Hall effect sensor6438 operates in conjunction with a magnet to provide a measurement ofan aperture defined by the jaw member 6434, which otherwise may bereferred to as a tissue gap, as shown with particularity in FIG. 19. Thesegmented flexible circuit 6430 may be employed to measure tissuethickness, force, displacement, compression, tissue impedance, andtissue location within an end effector.

FIG. 18 illustrates one aspect of a segmented flexible circuit 6440configured to mount to a jaw member 6444 of an end effector. Thesegmented flexible circuit 6580 comprises a distal segment 6442 a andlateral segments 6442 b, 6442 c that include individually addressablesensors for tissue control. The segments 6442 a, 6442 b, 6442 c areindividually addressable to treat tissue and to read individual sensorslocated within each of the segments 6442 a, 6442 b, 6442 c. The segments6442 a, 6442 b, 6442 c of the segmented flexible circuit 6440 aremounted to the jaw member 6444 and are electrically coupled to an energysource, via electrical conductive elements 6446. A Hall effect sensor6448, or other suitable magnetic sensor, is provided on a distal end ofthe jaw member 6444. The Hall effect sensor 6448 operates in conjunctionwith a magnet to provide a measurement of an aperture defined by the jawmember 6444 of the end effector or tissue gap as shown withparticularity in FIG. 19. In addition, a plurality of lateral asymmetrictemperature sensors 6450 a, 6450 b are mounted on or formally integrallywith the segmented flexible circuit 6440 to provide tissue temperaturefeedback to the control circuit. The segmented flexible circuit 6440 maybe employed to measure tissue thickness, force, displacement,compression, tissue impedance, and tissue location within an endeffector.

FIG. 19 illustrates one aspect of an end effector 6460 configured tomeasure a tissue gap G_(T). The end effector 6460 comprises a jaw member6462 and a jaw member 6444. The flexible circuit 6440 as described inFIG. 18 is mounted to the jaw member 6444. The flexible circuit 6440comprises a Hall effect sensor 6448 that operates with a magnet 6464mounted to the jaw member 6462 to measure the tissue gap G_(T). Thistechnique can be employed to measure the aperture defined between thejaw member 6444 and the jaw member 6462. The jaw member 6462 may be astaple cartridge.

FIG. 20 illustrates one aspect of an end effector 6470 comprisingsegmented flexible circuit 6468 as shown in FIG. 16. The end effector6470 comprises a jaw member 6472 and a staple cartridge 6474. Thesegmented flexible circuit 6468 is mounted to the jaw member 6472. Eachof the sensors disposed within the segments 1-5 are configured to detectthe presence of tissue positioned between the jaw member 6472 and thestaple cartridge 6474 and represent tissue zones 1-5. In theconfiguration shown in FIG. 20, the end effector 6470 is shown in anopen position ready to receive or grasp tissue between the jaw member6472 and the staple cartridge 6474. The segmented flexible circuit 6468may be employed to measure tissue thickness, force, displacement,compression, tissue impedance, and tissue location within the endeffector 6470.

FIG. 21 illustrates the end effector 6470 shown in FIG. 20 with the jawmember 6472 clamping tissue 6476 between the jaw members 6472, e.g., theanvil and the staple cartridge. As shown in FIG. 21, the tissue 6476 ispositioned between segments 1-3 and represents tissue zones 1-3.Accordingly, tissue 6476 is detected by the sensors in segments 1-3 andthe absence of tissue (empty) is detected in section 6478 by segments4-5. The information regarding the presence and absence of tissue 6476positioned within certain segments 1-3 and 4-5, respectively, iscommunicated to a control circuit as described herein via interfacecircuits, for example. The control circuit is configured to detecttissue located in segments 1-3. It will be appreciated that the segments1-5 may contain any suitable temperature, force/pressure, and/or Halleffect magnetic sensors to measure tissue parameters of tissue locatedwithin certain segments 1-5 and electrodes to deliver energy to tissuelocated in certain segments 1-5. The segmented flexible circuit 6468 maybe employed to measure tissue thickness, force, displacement,compression, tissue impedance, and tissue location within the endeffector 6470.

FIG. 22 illustrates a logic diagram of a feedback system 970 of therobotic surgical system 10 of FIG. 1 in accordance with one or moreaspects of the present disclosure. The system 970 comprises a circuit.The circuit includes a controller 961 comprising a processor 962 and amemory 968. One or more of sensors 972, 974, 976, such as, for example,provide real time feedback to the processor 962. A motor 982 driven by amotor driver 992 operably couples a longitudinally movable displacementmember to drive the I-beam knife element. A tracking system 980 isconfigured to determine the position of the longitudinally movabledisplacement member. The position information is provided to theprocessor 962, which can be programmed or configured to determine theposition of the longitudinally movable drive member as well as theposition of a firing member, firing bar, and I-beam knife element.Additional motors may be provided at the tool driver interface tocontrol I-beam firing, closure tube travel, shaft rotation, andarticulation.

In one form, a strain gauge can be used to measure the force applied tothe tissue by the end effector. A strain gauge can be coupled to the endeffector to measure the force on the tissue being treated by the endeffector. With reference now to FIG. 22, a system 970 for measuringforces applied to the tissue grasped by the end effector comprises astrain gauge sensor 972, such as, for example, a micro-strain gauge, isconfigured to measure one or more parameters of the end effector, forexample. In one aspect, the strain gauge sensor 972 can measure theamplitude or magnitude of the strain exerted on a jaw member of an endeffector during a clamping operation, which can be indicative of thetissue compression. The measured strain is converted to a digital signaland provided to a processor 962 of a microcontroller 961. A load sensor974 can measure the force to operate the knife element, for example, tocut the tissue captured between the anvil and the staple cartridge. Amagnetic field sensor 976 can be employed to measure the thickness ofthe captured tissue. The measurement of the magnetic field sensor 976also may be converted to a digital signal and provided to the processor962.

The measurements of the tissue compression, the tissue thickness, and/orthe force required to close the end effector on the tissue, asrespectively measured by the sensors 972, 974, 976, can be used by themicrocontroller 961 to characterize the selected position of the firingmember and/or the corresponding value of the speed of the firing member.In one instance, a memory 968 may store a technique, an equation, and/ora look-up table which can be employed by the microcontroller 961 in theassessment.

In the aspect illustrated in FIG. 22, a sensor 972, such as, forexample, a strain gauge or a micro-strain gauge, is configured tomeasure one or more parameters of the end effector 912, such as, forexample, the amplitude of the strain exerted on the anvil 914 during aclamping operation, which can be indicative of the closure forcesapplied to the anvil 914. The measured strain is converted to a digitalsignal and provided to the processor 962. Alternatively, or in additionto the sensor 972, a sensor 974, such as, for example, a load sensor,can measure the closure force applied by the closure drive system to theanvil 914. The sensor 976, such as, for example, a load sensor, canmeasure the firing force applied to an I-beam in a firing stroke of therobotic surgical system 10 (FIG. 1). The I-beam is configured to engagea wedge sled, which is configured to upwardly cam staple drivers toforce out staples into deforming contact with an anvil. The I-beam alsoincludes a sharpened cutting edge that can be used to sever tissue asthe I-beam is advanced distally by the firing bar. Alternatively, acurrent sensor 978 can be employed to measure the current drawn by themotor 982. The force required to advance the firing member 220 cancorrespond to the current drawn by the motor 982, for example. Themeasured force is converted to a digital signal and provided to theprocessor 962.

FIG. 23 illustrates a control circuit configured to control aspects ofthe robotic surgical system 10 according to one aspect of thisdisclosure. FIG. 23 illustrates a control circuit 800 configured tocontrol aspects of the robotic surgical system 10 according to oneaspect of this disclosure. The control circuit 800 can be configured toimplement various processes described herein. The control circuit 800may comprise a controller comprising one or more processors 802 (e.g.,microprocessor, microcontroller) coupled to at least one memory circuit804. The memory circuit 804 stores machine executable instructions thatwhen executed by the processor 802, cause the processor 802 to executemachine instructions to implement various processes described herein.The processor 802 may be any one of a number of single or multicoreprocessors known in the art. The memory circuit 804 may comprisevolatile and non-volatile storage media. The processor 802 may includean instruction processing unit 806 and an arithmetic unit 808. Theinstruction processing unit may be configured to receive instructionsfrom the memory circuit 804 of this disclosure.

FIG. 24 illustrates a combinational logic circuit 810 configured tocontrol aspects of the robotic surgical system 10 according to oneaspect of this disclosure. The combinational logic circuit 810 can beconfigured to implement various processes described herein. The circuit810 may comprise a finite state machine comprising a combinational logiccircuit 812 configured to receive data associated with the roboticsurgical system 10 at an input 814, process the data by thecombinational logic 812, and provide an output 816.

FIG. 25 illustrates a sequential logic circuit 820 configured to controlaspects of the robotic surgical system 10 according to one aspect ofthis disclosure. The sequential logic circuit 820 or the combinationallogic circuit 822 can be configured to implement various processesdescribed herein. The circuit 820 may comprise a finite state machine.The sequential logic circuit 820 may comprise a combinational logiccircuit 822, at least one memory circuit 824, and a clock 829, forexample. The at least one memory circuit 820 can store a current stateof the finite state machine. In certain instances, the sequential logiccircuit 820 may be synchronous or asynchronous. The combinational logiccircuit 822 is configured to receive data associated with the roboticsurgical system 10 an input 826, process the data by the combinationallogic circuit 822, and provide an output 828. In other aspects, thecircuit may comprise a combination of the processor 802 and the finitestate machine to implement various processes herein. In other aspects,the finite state machine may comprise a combination of the combinationallogic circuit 810 and the sequential logic circuit 820.

Aspects may be implemented as an article of manufacture. The article ofmanufacture may include a computer readable storage medium arranged tostore logic, instructions, and/or data for performing various operationsof one or more aspects. For example, the article of manufacture maycomprise a magnetic disk, optical disk, flash memory, or firmwarecontaining computer program instructions suitable for execution by ageneral purpose processor or application specific processor.

Referring primarily to FIG. 26 a robotic surgical system 10 may includea plurality of motors which can be activated to perform variousfunctions. In certain instances, a first motor can be activated toperform a first function; a second motor can be activated to perform asecond function; a third motor can be activated to perform a thirdfunction, a fourth motor can be activated to perform a fourth function,and so on. In certain instances, the plurality of motors of the roboticsurgical instrument 4400 can be individually activated to cause firing,closure and/or articulation motions in the end effector 1012. Thefiring, closure and/or articulation motions can be transmitted to theend effector 1012 through the shaft assembly 200, for example.

In certain instances, the robotic surgical system 10 may include afiring motor 4402. The firing motor 4402 may be operably coupled to afiring drive assembly 4404 which can be configured to transmit firingmotions generated by the motor 4402 to the end effector 1012, and inparticular to displace the I-beam element. In certain instances, thefiring motions generated by the motor 4402 may cause the staples to bedeployed from the staple cartridge into tissue captured by the endeffector and/or the cutting edge of the I-beam element to be advanced tocut the captured tissue, for example. The I-beam element may beretracted by reversing the direction of the motor 4402.

In certain instances, the robotic surgical system 10 may include aclosure motor 4403. The closure motor 4403 may be operably coupled to aclosure drive assembly 4405 which can be configured to transmit closuremotions generated by the motor 4403 to the end effector 1012, and inparticular to displace the closure tube 1040, 1042 to close the anvil1024 and compress tissue between the anvil 1024 and the staple cartridge1034. The closure motions may cause the end effector 1012 to transitionfrom an open configuration to an approximated configuration to capturetissue, for example. The end effector 102 may be transitioned to an openposition by reversing the direction of the motor 4403.

In certain instances, the robotic surgical instrument 10 may include oneor more articulation motors 4406 a, 4406 b, for example. The motors 4406a, 4406 b may be operably coupled to respective articulation driveassemblies 4408 a, 4408 b, which can be configured to transmitarticulation motions generated by the motors 4406 a, 4406 b to the endeffector 1012. In certain instances, the articulation motions may causethe end effector to articulate relative to the shaft, for example.

As described above, the robotic surgical instrument 10 may include aplurality of motors which may be configured to perform variousindependent functions. In certain instances, the plurality of motors ofthe robotic surgical instrument 10 can be individually or separatelyactivated to perform one or more functions while the other motors remaininactive. For example, the articulation motors 4406 a, 4406 b can beactivated to cause the end effector to be articulated while the firingmotor 4402 remains inactive. Alternatively, the firing motor 4402 can beactivated to fire the plurality of staples and/or advance the cuttingedge while the articulation motor 4406 remains inactive. Furthermore theclosure motor 4403 may be activated simultaneously with the firing motor4402 to cause the closure tube 1040, 1042 and the I-beam element toadvance distally as described in more detail hereinbelow.

In certain instances, the robotic surgical system 10 may include acommon control module 4410 which can be employed with a plurality ofmotors of the robotic surgical instrument 10. In certain instances, thecommon control module 4410 may accommodate one of the plurality ofmotors at a time. For example, the common control module 4410 can beseparably couplable to the plurality of motors of the robotic surgicalinstrument 10 individually. In certain instances, a plurality of themotors of the robotic surgical instrument 10 may share one or morecommon control modules such as the module 4410. In certain instances, aplurality of motors of the robotic surgical instrument 10 can beindividually and selectively engaged the common control module 4410. Incertain instances, the module 4410 can be selectively switched frominterfacing with one of a plurality of motors of the robotic surgicalinstrument 10 to interfacing with another one of the plurality of motorsof the robotic surgical instrument 10.

In at least one example, the module 4410 can be selectively switchedbetween operable engagement with the articulation motors 4406 a, 4406 band operable engagement with either the firing motor 4402 or the closuremotor 4403. In at least one example, as illustrated in FIG. 26, a switch4414 can be moved or transitioned between a plurality of positionsand/or states. In a first position 4416 the switch 4414 may electricallycouple the module 4410 to the firing motor 4402; in a second position4417, the switch 4414 may electrically couple the module 4410 to theclosure motor 4403; in a third position 4418 a the switch 4414 mayelectrically couple the module 4410 to the first articulation motor 4406a; and in a fourth position 4418 b the switch 4414 may electricallycouple the module 4410 to the second articulation motor 4406 b, forexample. In certain instances, separate modules 4410 can be electricallycoupled to the firing motor 4402, the closure motor 4403, and thearticulations motor 4406 a, 4406 b at the same time, as shown, forexample in FIG. 30. In certain instances, the switch 4414 may be amechanical switch, an electromechanical switch, a solid state switch, orany suitable switching mechanism.

Each of the motors 4402, 4403, 4406 a, 4406 b may comprise a torquesensor to measure the output torque on the shaft of the motor. The forceon an end effector may be sensed in any conventional manner such as byforce sensors on the outer sides of the jaws or by a torque sensor forthe motor actuating the jaws.

In various instances, as illustrated in FIG. 26, the common controlmodule 4410 may comprise a motor driver 4426 which may comprise one ormore H-Bridge field-effect transistors (FETs). The motor driver 4426 maymodulate the power transmitted from a power source 4428 to a motorcoupled to the module 4410 based on input from a microcontroller 4420(“controller”), for example. In certain instances, the controller 4420can be employed to determine the current drawn by the motor, forexample, while the motor is coupled to the module 4410, as describedabove.

In certain instances, the controller 4420 may include a microprocessor4422 (“processor”) and one or more computer readable mediums or memoryunits 4424 (“memory”). In certain instances, the memory 4424 may storevarious program instructions, which when executed may cause theprocessor 4422 to perform a plurality of functions and/or calculationsdescribed herein. In certain instances, one or more of the memory units4424 may be coupled to the processor 4422, for example.

In certain instances, the power source 4428 can be employed to supplypower to the controller 4420, for example. In certain instances, thepower source 4428 may comprise a battery (or “battery pack” or “powerpack”), such as a Li ion battery, for example. In certain instances, thebattery pack may be configured to be releasably mounted to the handle 14for supplying power to the surgical instrument 4400. A number of batterycells connected in series may be used as the power source 4428. Incertain instances, the power source 4428 may be replaceable and/orrechargeable, for example.

In various instances, the processor 4422 may control the motor driver4426 to control the position, direction of rotation, and/or velocity ofa motor that is coupled to the module 4410. In certain instances, theprocessor 4422 can signal the motor driver 4426 to stop and/or disable amotor that is coupled to the module 4410. It should be understood thatthe term processor as used herein includes any suitable microprocessor,microcontroller, or other basic computing device that incorporates thefunctions of a computer's central processing unit (CPU) on an integratedcircuit or at most a few integrated circuits. The processor is amultipurpose, programmable device that accepts digital data as input,processes it according to instructions stored in its memory, andprovides results as output. It is an example of sequential digitallogic, as it has internal memory. Processors operate on numbers andsymbols represented in the binary numeral system.

In one instance, the processor 4422 may be any single core or multicoreprocessor such as those known under the trade name ARM Cortex by TexasInstruments. In certain instances, the microcontroller 4420 may be an LM4F230H5QR, available from Texas Instruments, for example. In at leastone example, the Texas Instruments LM4F230H5QR is an ARM Cortex-M4FProcessor Core comprising on-chip memory of 256 KB single-cycle flashmemory, or other non-volatile memory, up to 40 MHz, a prefetch buffer toimprove performance above 40 MHz, a 32 KB single-cycle SRAM, internalROM loaded with StellarisWare® software, 2 KB EEPROM, one or more PWMmodules, one or more QEI analog, one or more 12-bit ADC with 12 analoginput channels, among other features that are readily available for theproduct datasheet. Other microcontrollers may be readily substituted foruse with the module 4410. Accordingly, the present disclosure should notbe limited in this context.

In certain instances, the memory 4424 may include program instructionsfor controlling each of the motors of the surgical instrument 4400 thatare couplable to the module 4410. For example, the memory 4424 mayinclude program instructions for controlling the firing motor 4402, theclosure motor 4403, and the articulation motors 4406 a, 4406 b. Suchprogram instructions may cause the processor 4422 to control the firing,closure, and articulation functions in accordance with inputs fromalgorithms or control programs of the robotic surgical system 10.

In certain instances, one or more mechanisms and/or sensors such as, forexample, sensors 4430 can be employed to alert the processor 4422 to theprogram instructions that should be used in a particular setting. Forexample, the sensors 4430 may alert the processor 4422 to use theprogram instructions associated with firing, closing, and articulatingthe end effector 1012. In certain instances, the sensors 4430 maycomprise position sensors which can be employed to sense the position ofthe switch 4414, for example. Accordingly, the processor 4422 may usethe program instructions associated with firing the I-beam of the endeffector 1012 upon detecting, through the sensors 4430 for example, thatthe switch 4414 is in the first position 4416; the processor 4422 mayuse the program instructions associated with closing the anvil upondetecting, through the sensors 4430 for example, that the switch 4414 isin the second position 4417; and the processor 4422 may use the programinstructions associated with articulating the end effector 1012 upondetecting, through the sensors 4430 for example, that the switch 4418 a,4418 b is in the third or fourth position 4418 a, 4418 b.

FIG. 27 is a diagram of an absolute positioning system 11100 of therobotic surgical instrument 10 where the absolute positioning system11100 comprises a controlled motor drive circuit arrangement comprisinga sensor arrangement 11102 according to one aspect of this disclosure.The sensor arrangement 11102 for an absolute positioning system 11100provides a unique position signal corresponding to the location of adisplacement member 11111. In one aspect the displacement member 11111represents the longitudinally movable drive member coupled to thecutting instrument or knife (e.g., cutting instrument 1032 in FIG. 11A,I-beam 3005 in FIG. 12, and/or I-beam 2514 in FIGS. 29-30) comprisingthe first knife driven gear 1226 in meshing engagement with the knifespur gear 1222, the second knife drive gear 1228 in meshing engagementwith a third knife drive gear 1230 that is rotatably supported on thetool mounting plate 302 in meshing engagement with the knife rack gear1206. In other aspects, the displacement member 11111 represents afiring member coupled to the cutting instrument or knife, which could beadapted and configured to include a rack of drive teeth. In yet anotheraspect, the displacement member 11111 represents a firing bar or theI-beam 3005, 2514 (FIGS. 12, 30), each of which can be adapted andconfigured to include a rack of drive teeth.

Accordingly, as used herein, the term displacement member is usedgenerically to refer to any movable member of the robotic surgicalinstrument 10 such as a drive member, firing member, firing bar, cuttinginstrument, knife, and/or I-beam, or any element that can be displaced.Accordingly, the absolute positioning system 11100 can, in effect, trackthe displacement of the cutting instrument I-beam 3005, 2514 (FIGS. 12,29-30) by tracking the displacement of a longitudinally movable drivemember. In various other aspects, the displacement member 11111 may becoupled to any sensor suitable for measuring displacement. Thus, alongitudinally movable drive member, firing member, the firing bar, or!-beam, or combinations thereof, may be coupled to any suitabledisplacement sensor. Displacement sensors may include contact ornon-contact displacement sensors. Displacement sensors may compriselinear variable differential transformers (LVDT), differential variablereluctance transducers (DVRT), a slide potentiometer, a magnetic sensingsystem comprising a movable magnet and a series of linearly arrangedHall effect sensors, a magnetic sensing system comprising a fixed magnetand a series of movable linearly arranged Hall effect sensors, anoptical sensing system comprising a movable light source and a series oflinearly arranged photo diodes or photo detectors, or an optical sensingsystem comprising a fixed light source and a series of movable linearlyarranged photo diodes or photo detectors, or any combination thereof.

An electric motor 11120 can include a rotatable shaft 11116 thatoperably interfaces with a gear assembly 11114 that is mounted inmeshing engagement with a set, or rack, of drive teeth on thedisplacement member 11111. A sensor element 11126 may be operablycoupled to a gear assembly 11114 such that a single revolution of thesensor element 11126 corresponds to some linear longitudinal translationof the displacement member 11111. An arrangement of gearing and sensors11118 can be connected to the linear actuator via a rack and pinionarrangement or a rotary actuator via a spur gear or other connection. Apower source 11129 supplies power to the absolute positioning system11100 and an output indicator 11128 may display the output of theabsolute positioning system 11100. The interface for adapting to themotor 11120 is shown in FIGS. 4-6, 8-10, and 11A, 11B.

A single revolution of the sensor element 11126 associated with theposition sensor 11112 is equivalent to a longitudinal displacement d1 ofthe of the displacement member 11111, where d1 is the longitudinaldistance that the displacement member 11111 moves from point “a” topoint “b” after a single revolution of the sensor element 11126 coupledto the displacement member 11111. The sensor arrangement 11102 may beconnected via a gear reduction that results in the position sensor 11112completing one or more revolutions for the full stroke of thedisplacement member 11111. The position sensor 11112 may completemultiple revolutions for the full stroke of the displacement member11111.

A series of switches 11122 a-11122 n, where n is an integer greater thanone, may be employed alone or in combination with gear reduction toprovide a unique position signal for more than one revolution of theposition sensor 11112. The state of the switches 11122 a-11122 n are fedback to a controller 11104 that applies logic to determine a uniqueposition signal corresponding to the longitudinal displacement d1+d2+ .. . dn of the displacement member 11111. The output 11124 of theposition sensor 11112 is provided to the controller 11104. The positionsensor 11112 of the sensor arrangement 11102 may comprise a magneticsensor, an analog rotary sensor like a potentiometer, an array of analogHall-effect elements, which output a unique combination of positionsignals or values. The controller 11104 may be contained within themaster controller 11 or may be contained within the tool mountingportion housing 301.

The absolute positioning system 11100 provides an absolute position ofthe displacement member 11111 upon power up of the robotic surgicalinstrument 10 without retracting or advancing the displacement member11111 to a reset (zero or home) position as may be required withconventional rotary encoders that merely count the number of stepsforwards or backwards that the motor 11120 has taken to infer theposition of a device actuator, drive bar, knife, and the like.

The controller 11104 may be programmed to perform various functions suchas precise control over the speed and position of the knife andarticulation systems. In one aspect, the controller 11104 includes aprocessor 11108 and a memory 11106. The electric motor 11120 may be abrushed DC motor with a gearbox and mechanical links to an articulationor knife system. In one aspect, a motor driver 11110 may be an A3941available from Allegro Microsystems, Inc. Other motor drivers may bereadily substituted for use in the absolute positioning system 11100.

The controller 11104 may be programmed to provide precise control overthe speed and position of the displacement member 11111 and articulationsystems. The controller 11104 may be configured to compute a response inthe software of the controller 11104. The computed response is comparedto a measured response of the actual system to obtain an “observed”response, which is used for actual feedback decisions. The observedresponse is a favorable, tuned, value that balances the smooth,continuous nature of the simulated response with the measured response,which can detect outside influences on the system.

The absolute positioning system 11100 may comprise and/or be programmedto implement a feedback controller, such as a PID, state feedback, andadaptive controller. A power source 11129 converts the signal from thefeedback controller into a physical input to the system, in this casevoltage. Other examples include pulse width modulation (PWM) of thevoltage, current, and force. Other sensor(s) 11118 may be provided tomeasure physical parameters of the physical system in addition toposition measured by the position sensor 11112. In a digital signalprocessing system, absolute positioning system 1100 is coupled to adigital data acquisition system where the output of the absolutepositioning system 11100 will have finite resolution and samplingfrequency. The absolute positioning system 11100 may comprise a compareand combine circuit to combine a computed response with a measuredresponse using algorithms such as weighted average and theoreticalcontrol loop that drives the computed response towards the measuredresponse. The computed response of the physical system takes intoaccount properties like mass, inertial, viscous friction, inductanceresistance, etc., to predict what the states and outputs of the physicalsystem will be by knowing the input.

The motor driver 11110 may be an A3941 available from AllegroMicrosystems, Inc. The A3941 driver 11110 is a full-bridge controllerfor use with external N-channel power metal oxide semiconductor fieldeffect transistors (MOSFETs) specifically designed for inductive loads,such as brush DC motors. The driver 11110 comprises a unique charge pumpregulator provides full (>10 V) gate drive for battery voltages down to7 V and allows the A3941 to operate with a reduced gate drive, down to5.5 V. A bootstrap capacitor may be employed to provide theabove-battery supply voltage required for N-channel MOSFETs. An internalcharge pump for the high-side drive allows DC (100% duty cycle)operation. The full bridge can be driven in fast or slow decay modesusing diode or synchronous rectification. In the slow decay mode,current recirculation can be through the high-side or the lowside FETs.The power FETs are protected from shoot-through by resistor adjustabledead time. Integrated diagnostics provide indication of undervoltage,overtemperature, and power bridge faults, and can be configured toprotect the power MOSFETs under most short circuit conditions. Othermotor drivers may be readily substituted for use in the absolutepositioning system 11100.

FIG. 28 is a diagram of a position sensor 11200 for an absolutepositioning system 11100 comprising a magnetic rotary absolutepositioning system according to one aspect of this disclosure. Theposition sensor 11200 may be implemented as an AS5055EQFT single-chipmagnetic rotary position sensor available from Austria Microsystems, AG.The position sensor 11200 is interfaced with the controller 11104 toprovide an absolute positioning system 11100. The position sensor 11200is a low-voltage and low-power component and includes four Hall-effectelements 11228A, 11228B, 11228C, 11228D in an area 11230 of the positionsensor 11200 that is located above a magnet 11202 positioned on arotating element associated with a displacement member such as, forexample, the knife drive gear 1228, 1230 and/or the closure drive gear1118, 1120 such that the displacement of a firing member and/or aclosure member can be precisely tracked. A high-resolution ADC 11232 anda smart power management controller 11238 are also provided on the chip.A CORDIC processor 11236 (for Coordinate Rotation Digital Computer),also known as the digit-by-digit method and Volder's algorithm, isprovided to implement a simple and efficient algorithm to calculatehyperbolic and trigonometric functions that require only addition,subtraction, bitshift, and table lookup operations. The angle position,alarm bits, and magnetic field information are transmitted over astandard serial communication interface such as an SPI interface 11234to the controller 11104. The position sensor 11200 provides 12 or 14bits of resolution. The position sensor 11200 may be an AS5055 chipprovided in a small QFN 16-pin 4×4×0.85 mm package.

The Hall-effect elements 11228A, 11228B, 11228C, 11228D are locateddirectly above the rotating magnet 11202. The Hall-effect is awell-known effect and for expediency will not be described in detailherein, however, generally, the Hall-effect produces a voltagedifference (the Hall voltage) across an electrical conductor transverseto an electric current in the conductor and a magnetic fieldperpendicular to the current. A Hall coefficient is defined as the ratioof the induced electric field to the product of the current density andthe applied magnetic field. It is a characteristic of the material fromwhich the conductor is made, since its value depends on the type,number, and properties of the charge carriers that constitute thecurrent. In the AS5055 position sensor 11200, the Hall-effect elements11228A, 11228B, 11228C, 11228D are capable producing a voltage signalthat is indicative of the absolute position of the magnet 11202 in termsof the angle over a single revolution of the magnet 11202. This value ofthe angle, which is unique position signal, is calculated by the CORDICprocessor 11236 is stored onboard the AS5055 position sensor 11200 in aregister or memory. The value of the angle that is indicative of theposition of the magnet 11202 over one revolution is provided to thecontroller 11104 in a variety of techniques, e.g., upon power up or uponrequest by the controller 11104.

The AS5055 position sensor 11200 requires only a few external componentsto operate when connected to the controller 11104. Six wires are neededfor a simple application using a single power supply: two wires forpower and four wires 11240 for the SPI interface 11234 with thecontroller 11104. A seventh connection can be added in order to send aninterrupt to the controller 11104 to inform that a new valid angle canbe read. Upon power-up, the AS5055 position sensor 11200 performs a fullpower-up sequence including one angle measurement. The completion ofthis cycle is indicated as an INT output 11242, and the angle value isstored in an internal register. Once this output is set, the AS5055position sensor 11200 suspends to sleep mode. The controller 11104 canrespond to the INT request at the INT output 11242 by reading the anglevalue from the AS5055 position sensor 11200 over the SPI interface11234. Once the angle value is read by the controller 11104, the INToutput 11242 is cleared again. Sending a “read angle” command by the SPIinterface 11234 by the controller 11104 to the position sensor 11200also automatically powers up the chip and starts another anglemeasurement. As soon as the controller 11104 has completed reading ofthe angle value, the INT output 11242 is cleared and a new result isstored in the angle register. The completion of the angle measurement isagain indicated by setting the INT output 11242 and a corresponding flagin the status register.

Due to the measurement principle of the AS5055 position sensor 11200,only a single angle measurement is performed in very short time (˜600μs) after each power-up sequence. As soon as the measurement of oneangle is completed, the AS5055 position sensor 11200 suspends topower-down state. An on-chip filtering of the angle value by digitalaveraging is not implemented, as this would require more than one anglemeasurement and, consequently, a longer power-up time that is notdesired in low-power applications. The angle jitter can be reduced byaveraging of several angle samples in the controller 11104. For example,an averaging of four samples reduces the jitter by 6 dB (50%).

FIG. 29 is a section view of an end effector 2502 of the roboticsurgical instrument 10 showing an I-beam 2514 firing stroke relative totissue 2526 grasped within the end effector 2502 according to one aspectof this disclosure. The end effector 2502 is configured to operate withthe surgical instrument 10. The end effector 2502 comprises an anvil2516 and an elongated channel 2503 with a staple cartridge 2518positioned in the elongated channel 2503. A firing bar 2520 istranslatable distally and proximally along a longitudinal axis 2515 ofthe end effector 2502. When the end effector 2502 is not articulated,the end effector 2502 is in line with the shaft of the instrument. AnI-beam 2514 comprising a cutting edge 2509 is illustrated at a distalportion of the firing bar 2520. A wedge sled 2513 is positioned in thestaple cartridge 2518. As the I-beam 2514 translates distally, thecutting edge 2509 contacts and may cut tissue 2526 positioned betweenthe anvil 2516 and the staple cartridge 2518. Also, the I-beam 2514contacts the wedge sled 2513 and pushes it distally, causing the wedgesled 2513 to contact staple drivers 2511. The staple drivers 2511 may bedriven up into staples 2505, causing the staples 2505 to advance throughtissue and into pockets 2507 defined in the anvil 2516, which shape thestaples 2505.

An example I-beam 2514 firing stroke is illustrated by a chart 2529aligned with the end effector 2502. Example tissue 2526 is also shownaligned with the end effector 2502. The firing member stroke maycomprise a stroke begin position 2527 and a stroke end position 2528.During an I-beam 2514 firing stroke, the I-beam 2514 may be advanceddistally from the stroke begin position 2527 to the stroke end position2528. The I-beam 2514 is shown at one example location of a stroke beginposition 2527. The I-beam 2514 firing member stroke chart 2529illustrates five firing member stroke regions 2517, 2519, 2521, 2523,2525. In a first firing stroke region 2517, the I-beam 2514 may begin toadvance distally. In the first firing stroke region 2517, the I-beam2514 may contact the wedge sled 2513 and begin to move it distally.While in the first region, however, the cutting edge 2509 may notcontact tissue and the wedge sled 2513 may not contact a staple driver2511. After static friction is overcome, the force to drive the !-beam2514 in the first region 2517 may be substantially constant.

In the second firing member stroke region 2519, the cutting edge 2509may begin to contact and cut tissue 2526. Also, the wedge sled 2513 maybegin to contact staple drivers 2511 to drive staples 2505. Force todrive the I-beam 2514 may begin to ramp up. As shown, tissue encounteredinitially may be compressed and/or thinner because of the way that theanvil 2516 pivots relative to the staple cartridge 2518. In the thirdfiring member stroke region 2521, the cutting edge 2509 may continuouslycontact and cut tissue 2526 and the wedge sled 2513 may repeatedlycontact staple drivers 2511. Force to drive the I-beam 2514 may plateauin the third region 2521. By the fourth firing stroke region 2523, forceto drive the I-beam 2514 may begin to decline. For example, tissue inthe portion of the end effector 2502 corresponding to the fourth firingregion 2523 may be less compressed than tissue closer to the pivot pointof the anvil 2516, requiring less force to cut. Also, the cutting edge2509 and wedge sled 2513 may reach the end of the tissue 2526 while inthe fourth region 2523. When the I-beam 2514 reaches the fifth region2525, the tissue 2526 may be completely severed. The wedge sled 2513 maycontact one or more staple drivers 2511 at or near the end of thetissue. Force to advance the I-beam 2514 through the fifth region 2525may be reduced and, in some examples, may be similar to the force todrive the I-beam 2514 in the first region 2517. At the conclusion of thefiring member stroke, the I-beam 2514 may reach the stroke end position2528. The positioning of firing member stroke regions 2517, 2519, 2521,2523, 2525 in FIG. 29 is just one example. In some examples, differentregions may begin at different positions along the end effectorlongitudinal axis 2515, for example, based on the positioning of tissuebetween the anvil 2516 and the staple cartridge 2518.

As discussed above and with reference now to FIGS. 27-29, the electricmotor 11122 positioned within the master controller 13 of the surgicalinstrument 10 can be utilized to advance and/or retract the firingsystem of the shaft assembly, including the I-beam 2514, relative to theend effector 2502 of the shaft assembly in order to staple and/or incisetissue captured within the end effector 2502. The I-beam 2514 may beadvanced or retracted at a desired speed, or within a range of desiredspeeds. The controller 1104 may be configured to control the speed ofthe I-beam 2514. The controller 11104 may be configured to predict thespeed of the I-beam 2514 based on various parameters of the powersupplied to the electric motor 11122, such as voltage and/or current,for example, and/or other operating parameters of the electric motor11122 or external influences. The controller 11104 may be configured topredict the current speed of the I-beam 2514 based on the previousvalues of the current and/or voltage supplied to the electric motor11122, and/or previous states of the system like velocity, acceleration,and/or position. The controller 11104 may be configured to sense thespeed of the I-beam 2514 utilizing the absolute positioning sensorsystem described herein. The controller can be configured to compare thepredicted speed of the I-beam 2514 and the sensed speed of the I-beam2514 to determine whether the power to the electric motor 11122 shouldbe increased in order to increase the speed of the I-beam 2514 and/ordecreased in order to decrease the speed of the I-beam 2514.

Force acting on the I-beam 2514 may be determined using varioustechniques. The I-beam 2514 force may be determined by measuring themotor 2504 current, where the motor 2504 current is based on the loadexperienced by the I-beam 2514 as it advances distally. The I-beam 2514force may be determined by positioning a strain gauge on the drivemember, the firing member, I-beam 2514, the firing bar, and/or on aproximal end of the cutting edge 2509. The I-beam 2514 force may bedetermined by monitoring the actual position of the I-beam 2514 movingat an expected velocity based on the current set velocity of the motor11122 after a predetermined elapsed period T₁ and comparing the actualposition of the I-beam 2514 relative to the expected position of theI-beam 2514 based on the current set velocity of the motor 11122 at theend of the period T₁. Thus, if the actual position of the I-beam 2514 isless than the expected position of the I-beam 2514, the force on theI-beam 2514 is greater than a nominal force. Conversely, if the actualposition of the I-beam 2514 is greater than the expected position of theI-beam 2514, the force on the I-beam 2514 is less than the nominalforce. The difference between the actual and expected positions of theI-beam 2514 is proportional to the deviation of the force on the I-beam2514 from the nominal force.

FIG. 30 is a schematic diagram of a robotic surgical instrument 2500configured to operate the surgical tool described herein according toone aspect of this disclosure. The robotic surgical instrument 2500 maybe programmed or configured to control distal/proximal translation of adisplacement member, closure tube distal/proximal displacement, shaftrotation, and articulation, either with single or multiple articulationdrive links. In one aspect, the surgical instrument 2500 may beprogrammed or configured to individually control a firing member, aclosure member, a shaft member, and/or one or more articulation members.The surgical instrument 2500 comprises a control circuit 2510 configuredto control motor-driven firing members, closure members, shaft members,and/or one or more articulation members.

In one aspect, the robotic surgical instrument 2500 comprises a controlcircuit 2510 configured to control an anvil 2516 and an I-beam 2514(including a sharp cutting edge) portion of an end effector 2502, aremovable staple cartridge 2518, a shaft 2540, and one or morearticulation members 2542 a, 2542 b via a plurality of motors 2504a-2504 e. A position sensor 2534 may be configured to provide positionfeedback of the I-beam 2514 to the control circuit 2510. Other sensors2538 may be configured to provide feedback to the control circuit 2510.A timer/counter 2531 provides timing and counting information to thecontrol circuit 2510. An energy source 2512 may be provided to operatethe motors 2504 a-2504 e and a current sensor 2536 provides motorcurrent feedback to the control circuit 2510. The motors 2504 a-2504 ecan be individually operated by the control circuit 2510 in open loop orclosed loop feedback control.

In one aspect, the control circuit 2510, may comprise one or moremicrocontrollers, microprocessors, or other suitable processors forexecuting instructions that cause the processor or processors. Thecontrol circuit 2510 may be implemented as control circuit 961 (FIG.22), 800 (FIG. 23), 810 (FIG. 24), 820 (FIG. 25), 4420 (FIG. 26). In oneaspect, a timer/counter circuit 2531 provides an output signal, such aselapsed time or a digital count, to the control circuit 2510 tocorrelate the position of the I-beam 2514 as determined by the positionsensor 2534 with the output of the timer/counter circuit 2531 such thatthe control circuit 2510 can determine the position of the I-beam 2514at a specific time (t) relative to a starting position or the time (t)when the I-beam 2514 is at a specific position relative to a startingposition. The timer/counter circuit 2531 may be configured to measureelapsed time, count external evens, or time external events.

In one aspect, the control circuit 2510 may be programmed to controlfunctions of the end effector 2502 based on one or more tissueconditions. The control circuit 2510 may be programmed to sense tissueconditions, such as thickness, either directly or indirectly, asdescribed herein. The control circuit 2510 may be programmed to select afiring control program or closure control program based on tissueconditions. A firing control program may describe the distal motion ofthe displacement member. Different firing control programs may beselected to better treat different tissue conditions. For example, whenthicker tissue is present, the control circuit 2510 may be programmed totranslate the displacement member at a lower velocity and/or with lowerpower. When thinner tissue is present, the control circuit 2510 may beprogrammed to translate the displacement member at a higher velocityand/or with higher power. A closure control program may control theclosure force applied to the tissue by the anvil 2516. Other controlprograms control the rotation of the shaft 2540 and the articulationmembers 2542 a, 2542 b.

In one aspect, the control circuit 2510 may generate motor set pointsignals. The motor set point signals may be provided to various motorcontrollers 2508 a-2508 e. The motor controllers 2508 a-2508 e maycomprise one or more circuits configured to provide motor drive signalsto the motors 2504 a-2504 e to drive the motors 2504 a-2504 e asdescribed herein. In some examples, the motors 2504 a-2504 e may bebrushed DC electric motors. For example, the velocity of the motors 2504a-2504 e may be proportional to the respective motor drive signals. Insome examples, the motors 2504 a-2540 e may be brushless direct current(DC) electric motors and the respective motor drive signals 2524 a-2524e may comprise a pulse-width-modulated (PWM) signal provided to one ormore stator windings of the motors 2504 a-2504 e. Also, in someexamples, the motor controllers 2508 a-2508 e may be omitted and thecontrol circuit 2510 may generate the motor drive signals 2524 a-2524 edirectly.

In one aspect, the control circuit 2510 may initially operate each ofthe motors 2504 a-2504 e in an open-loop configuration for a firstopen-loop portion of a stroke of the displacement member. Based on aresponse of the instrument 2500 during the open-loop portion of thestroke, the control circuit 2510 may select a firing control program ina closed-loop configuration. The response of the instrument may include,a translation distance of the displacement member during the open-loopportion, a time elapsed during the open-loop portion, energy provided tothe motor 2504 during the open-loop portion, a sum of pulse widths of amotor drive signal, etc. After the open-loop portion, the controlcircuit 2510 may implement the selected firing control program for asecond portion of the displacement member stroke. For example, during aclosed loop portion of the stroke, the control circuit 2510 may modulatethe motor 2504 based on translation data describing a position of thedisplacement member in a closed-loop manner to translate thedisplacement member at a constant velocity.

In one aspect, the motors 2504 a-2504 e may receive power from an energysource 2512. The energy source 2512 may be a DC power supply driven by amain AC power source, a battery, a super capacitor, or any othersuitable energy source 2512. The motors 2504 a-2504 e may bemechanically coupled to individual movable mechanical elements such asthe I-beam 2514, anvil 2516, shaft 2540, articulation 2542 a,articulation 2542 b via respective transmissions 2506 a-2506 e. Thetransmissions 2506 a-2506 e may include one or more gears or otherlinkage components to couple the motors 2504 a-2504 e to movablemechanical elements. A position sensor 2534 may sense a position of theI-beam 2514. The position sensor 2534 may be or include any type ofsensor that is capable of generating position data that indicates aposition of the I-beam 2514. In some examples, the position sensor 2534may include an encoder configured to provide a series of pulses to thecontrol circuit 2510 as the I-beam 2514 translates distally andproximally. The control circuit 2510 may track the pulses to determinethe position of the I-beam 2514. Other suitable position sensor may beused, including, for example, a proximity sensor. Other types ofposition sensors may provide other signals indicating motion of theI-beam 2514. Also, in some examples, the position sensor 2534 may beomitted. Where any of the motors 2504 a-2504 e is a stepper motor, thecontrol circuit 2510 may track the position of the I-beam 2514 byaggregating the number and direction of steps that the motor 2504 hasbeen instructed to execute. The position sensor 2534 may be located inthe end effector 2502 or at any other portion of the instrument. Theoutputs of each of the motors 2504 a-2504 e includes a torque sensor2544 a-2544 e to sense force and has an encoder to sense rotation of thedrive shaft.

In one aspect, the control circuit 2510 is configured to drive a firingmember such as the I-beam 2514 portion of the end effector 2502. Thecontrol circuit 2510 provides a motor set point to a motor control 2508a, which provides a drive signal to the motor 2504 a. The output shaftof the motor 2504 a is coupled to a torque sensor 2544 a and atransmission 2506 a which is coupled to the I-beam 2514. Thetransmission 2506 a comprises movable mechanical elements such asrotating elements and a firing member to control the movement of theI-beam 2514 distally and proximally along a longitudinal axis of the endeffector 2502. In one aspect, the motor 2504 a may be coupled to theknife gear assembly 1220, which includes a knife gear reduction set 1224that includes a first knife drive gear 1226 and a second knife drivegear 1228. As can be seen in FIGS. 9 and 10, the knife gear reductionset 1224 is rotatably mounted to the tool mounting plate 302 such thatthe first knife drive gear 1226 is in meshing engagement with the knifespur gear 1222. Likewise, the second knife drive gear 1228 is in meshingengagement with a third knife drive gear 1230 that is rotatablysupported on the tool mounting plate 302 in meshing engagement with theknife rack gear 1206. A torque sensor 2544 a provides a firing forcefeedback signal to the control circuit 2510. The firing force signalrepresents the force required to fire or displace the I-beam 2514. Aposition sensor 2534 may be configured to provide the position of theI-beam 2514 along the firing stroke or the position of the firing memberas a feedback signal to the control circuit 2510. The end effector 2502may include additional sensors 2538 configured to provide feedbacksignals to the control circuit 2510. When ready to use, the controlcircuit 2510 may provide a firing signal to the motor control 2508 a. Inresponse to the firing signal, the motor 2504 a may drive the firingmember distally along the longitudinal axis of the end effector 2502from a proximal stroke begin position to a stroke end position distal ofthe stroke begin position. As the firing member translates distally, anI-beam 2514 with a cutting element positioned at a distal end, advancesdistally to cut tissue located between the staple cartridge 2518 and theanvil 2516.

In one aspect, the control circuit 2510 is configured to drive a closuremember such as the anvil 2516 portion of the end effector 2502. Thecontrol circuit 2510 provides a motor set point to a motor control 2508b, which provides a drive signal to the motor 2504 b. The output shaftof the motor 2504 b is coupled to a torque sensor 2544 b and atransmission 2506 b which is coupled to the anvil 2516. The transmission2506 b comprises movable mechanical elements such as rotating elementsand a closure member to control the movement of the anvil 2516 from openand closed positions. In one aspect, the motor 2504 b is coupled to theclosure gear assembly 1110, which includes a closure reduction gear set1114 that is supported in meshing engagement with the closure spur gear1112. As can be seen in FIGS. 9 and 10, the closure reduction gear set1114 includes a driven gear 1116 that is rotatably supported in meshingengagement with the closure spur gear 1112. The closure reduction gearset 1114 further includes a first closure drive gear 1118 that is inmeshing engagement with a second closure drive gear 1120 that isrotatably supported on the tool mounting plate 302 in meshing engagementwith the closure rack gear 1106. The torque sensor 2544 b provides aclosure force feedback signal to the control circuit 2510. The closureforce feedback signal represents the closure force applied to the anvil2516. The position sensor 2534 may be configured to provide the positionof the closure member as a feedback signal to the control circuit 2510.Additional sensors 2538 in the end effector 2502 may provide the closureforce feedback signal to the control circuit 2510. The pivotable anvil2516 is positioned opposite the staple cartridge 2518. When ready touse, the control circuit 2510 may provide a closure signal to the motorcontrol 2508 b. In response to the closure signal, the motor 2504 badvances a closure member to grasp tissue between the anvil 2516 and thestaple cartridge 2518.

In one aspect, the control circuit 2510 is configured to rotate a shaftmember such as the shaft 2540 to rotate the end effector 2502. Thecontrol circuit 2510 provides a motor set point to a motor control 2508c, which provides a drive signal to the motor 2504 c. The output shaftof the motor 2504 c is coupled to a torque sensor 2544 c and atransmission 2506 c which is coupled to the shaft 2540. The transmission2506 c comprises movable mechanical elements such as rotating elementsto control the rotation of the shaft 2540 clockwise or counterclockwiseup to and over 360°. In one aspect, the motor 2504 c is coupled to therotational transmission assembly 1069, which includes a tube gearsegment 1062 that is formed on (or attached to) the proximal end 1060 ofthe proximal closure tube 1040 for operable engagement by a rotationalgear assembly 1070 that is operably supported on the tool mounting plate302. As shown in FIG. 8, the rotational gear assembly 1070, in at leastone aspect, comprises a rotation drive gear 1072 that is coupled to acorresponding first one of the driven discs or elements 304 on theadapter side 307 of the tool mounting plate 302 when the tool mountingportion 300 is coupled to the tool drive assembly 101. See FIG. 6. Therotational gear assembly 1070 further comprises a rotary driven gear1074 that is rotatably supported on the tool mounting plate 302 inmeshing engagement with the tube gear segment 1062 and the rotationdrive gear 1072. The torque sensor 2544 c provides a rotation forcefeedback signal to the control circuit 2510. The rotation force feedbacksignal represents the rotation force applied to the shaft 2540. Theposition sensor 2534 may be configured to provide the position of theclosure member as a feedback signal to the control circuit 2510.Additional sensors 2538 such as a shaft encoder may provide therotational position of the shaft 2540 to the control circuit 2510.

In one aspect, the control circuit 2510 is configured to articulate theend effector 2502. The control circuit 2510 provides a motor set pointto a motor control 2508 d, which provides a drive signal to the motor2504 d. The output shaft of the motor 2504 d is coupled to a torquesensor 2544 d and a transmission 2506 d which is coupled to anarticulation member 2542 a. The transmission 2506 d comprises movablemechanical elements such as articulation elements to control thearticulation of the end effector 2502±65°. In one aspect, the motor 2504d is coupled to the articulation nut 1260, which is rotatably journaledon the proximal end portion of the distal spine portion 1050 and isrotatably driven thereon by an articulation gear assembly 1270. Morespecifically and with reference to FIG. 8, in at least one aspect, thearticulation gear assembly 1270 includes an articulation spur gear 1272that is coupled to a corresponding fourth one of the driven discs orelements 304 on the adapter side 307 of the tool mounting plate 302. Thetorque sensor 2544 d provides an articulation force feedback signal tothe control circuit 2510. The articulation force feedback signalrepresents the articulation force applied to the end effector 2502.Sensors 2538 such as an articulation encoder may provide thearticulation position of the end effector 2502 to the control circuit2510.

In another aspect, the articulation function of the robotic surgicalsystem 10 may comprise two drive members 2542 a, 2542 b or links. Thesedrive members 2542 a, 2542 b are driven by separate disks on the robotinterface (the rack) which are driven by the two motors 2508 d, 2508 e.When the separate firing motor 2504 a is provided, each articulationlink 2542 a, 2542 b can be antagonistically driven with respect to theother link in order to provide resistive holding motion and load to thehead when it is not moving and to provide articulation motion as thehead is articulated. The drive members 2542 a, 2542 b or links attach tothe head at a fixed radius as the head is rotated. Accordingly, themechanical advantage of the push and pull link changes as the head isrotated. This change in the mechanical advantage may be more pronouncedwith other articulation link drive systems.

In one aspect, the end effector 2502 may be implemented as the surgicalend effector 1012, 3000, 5650, 6460, 6470 shown and described inconnection with FIGS. 4, 6, 8-12, 15A, 15B, 19, 20, and 21. In oneaspect, the I-beam 2514 portion of the end effector 2502 may beimplemented as the knife member 1032, 3005, 2514 shown and described inconnection with FIGS. 11A, 12, 29. The I-beam 2514 comprises a knifebody that operably supports a tissue cutting blade 2509 (FIG. 29)thereon. In one aspect, the anvil 2516 portion of the end effector 2502may be implemented as the anvil 1024, 3002, 5502, 5602, 6472 shown anddescribed in connection with FIGS. 4, 6-14, 20, and 21.

In one aspect, the one or more motors 2504 a-2504 e may comprise abrushed DC motor with gearbox and mechanical links to a firing member,closure member, or articulation member. Another example are electricmotors 2504 a-2504 e that operate the movable mechanical elements suchas the displacement member, articulation links, closure tube, and shaft.An outside influence is an unmeasured, unpredictable influence of thingslike tissue, surrounding bodies and friction on the physical system.Such outside influence can be referred to as drag which acts inopposition to an electric motor 2504 a-2504 e. The outside influence,such as drag, may cause the operation of the physical system to deviatefrom a desired operation of the physical system.

In one aspect, the position sensor 2534 may be implemented as anabsolute positioning system as shown and described in connection withFIGS. 27 and 28. In one aspect, the position sensor 2534 may comprise amagnetic rotary absolute positioning system implemented as an AS5055EQFTsingle-chip magnetic rotary position sensor available from AustriaMicrosystems, AG. The position sensor 2534 may interface with thecontrol circuit 2510 to provide an absolute positioning system. Theposition may include multiple Hall-effect elements located above amagnet and coupled to a CORDIC processor (for Coordinate RotationDigital Computer), also known as the digit-by-digit method and Volder'salgorithm, is provided to implement a simple and efficient algorithm tocalculate hyperbolic and trigonometric functions that require onlyaddition, subtraction, bitshift, and table lookup operations.

In one aspect, the control circuit 2510 may be in communication with oneor more sensors 2538. The sensors 2538 may be positioned on the endeffector 2502 and adapted to operate with the surgical instrument 2500to measure the various derived parameters such as gap distance versustime, tissue compression versus time, and anvil strain versus time. Thesensors 2538 may comprise a magnetic sensor, a magnetic field sensor, astrain gauge, a load cell, a pressure sensor, a force sensor, a torquesensor, an inductive sensor such as an eddy current sensor, a resistivesensor, a capacitive sensor, an optical sensor, and/or any othersuitable sensor for measuring one or more parameters of the end effector2502. The sensors 2538 may include one or more sensors. The sensors 2538may be located on the staple cartridge 2518 deck to determine tissuelocation using segmented electrodes. The torque sensors 2544 a-2544 emay be configured to sense force such as firing force, closure force,articulation force, among others. Accordingly, the control circuit 26510can sense: (1) the closure load experienced by the distal closure tubeand its position; (2) the firing member at the rack and its position;(3) what portion of the staple cartridge 2518 has tissue on it; and (4)sense the load and position on both articulation rods.

In one aspect, the one or more sensors 2538 may comprise a strain gauge,such as a micro-strain gauge, configured to measure the magnitude of thestrain in the anvil 2516 during a clamped condition. The strain gaugeprovides an electrical signal whose amplitude varies with the magnitudeof the strain. The sensors 2538 may comprise a pressure sensorconfigured to detect a pressure generated by the presence of compressedtissue between the anvil 2516 and the staple cartridge 2518. The sensors2538 may be configured to detect impedance of a tissue section locatedbetween the anvil 2516 and the staple cartridge 2518 that is indicativeof the thickness and/or fullness of tissue located therebetween.

In one aspect, the sensors 2538 may be implemented as one or more limitswitches, electromechanical devices, solid state switches, Hall-effectdevices, magneto-resistive (MR) devices, giant magneto-resistive (GMR)devices, magnetometers, among others. In other implementations, thesensors 2538 may be implemented as solid state switches that operateunder the influence of light, such as optical sensors, infrared sensors,ultraviolet sensors, among others. Still, the switches may be solidstate devices such as transistors (e.g., FET, Junction-FET, metal-oxidesemiconductor-FET (MOSFET), bipolar, and the like). In otherimplementations, the sensors 2538 may include electrical conductorlessswitches, ultrasonic switches, accelerometers, inertial sensors, amongothers.

In one aspect, the sensors 2538 may be configured to measure forcesexerted on the anvil 2516 by the closure drive system. For example, oneor more sensors 2538 can be at an interaction point between the closuretube and the anvil 2516 to detect the closure forces applied by theclosure tube to the anvil 2516. The forces exerted on the anvil 2516 canbe representative of the tissue compression experienced by the tissuesection captured between the anvil 2516 and the staple cartridge 2518.The one or more sensors 2538 can be positioned at various interactionpoints along the closure drive system to detect the closure forcesapplied to the anvil 2516 by the closure drive system. The one or moresensors 2538 may be sampled in real time during a clamping operation bythe processor of the control circuit 2510. The control circuit 2510receives real-time sample measurements to provide analyze time basedinformation and assess, in real time, closure forces applied to theanvil 2516.

In one aspect, a current sensor 2536 can be employed to measure thecurrent drawn by each of the motors 2504 a-2504 e. The force required toadvance any of the movable mechanical elements such as the I-beam 2514corresponds to the current drawn by a motor 2504 a-2504 e. The force isconverted to a digital signal and provided to the control circuit 2510.The control circuit 2510 can be configured to simulate the response ofthe actual system of the instrument in the software of the controller. Adisplacement member can be actuated to move an I-beam 2514 in the endeffector 2502 at or near a target velocity. The robotic surgicalinstrument 2500 can include a feedback controller, which can be one ofany feedback controllers, including, but not limited to a PID, a StateFeedback, LQR, and/or an Adaptive controller, for example. The roboticsurgical instrument 2500 can include a power source to convert thesignal from the feedback controller into a physical input such as casevoltage, pulse width modulated (PWM) voltage, frequency modulatedvoltage, current, torque, and/or force, for example.

In some aspects, a control algorithm is provided for manipulating a pairof articulation arms configured to control an articulation angle of anend effector of the robotic surgical instrument. Other aspects of thepresent disclosure focus on the robotic arm system, including the pairof articulation arms coupled to the end effector and guided byindependent motors, e.g., motors 2504 d and 2504 e. The two articulationarms are designed to exert antagonistic forces competing against oneanother and whose magnitudes are apportioned according to a ratiospecified in the control algorithm. The ratio of the antagonistic forcesmay be used to determine the articulation angle of the head or endeffector of the robotic surgical arm. In one aspect the presentdisclosure provides control algorithms to reliably govern the movementsof two or more of these components when there is an interrelationship.

Referring to FIG. 31, illustration 13500 shows an example structuralportion of a robotic surgical arm including two articulation armsconnected to an end effector, according to some aspects of the presentdisclosure. Here, the end effector includes an anvil 13502 connected toright articulation arm 13504 and left articulation arm 13506. The rightarticulation arm 13504 includes a right articulation link 13508 and aright articulation bar 13510. These two components are connected via ahinge as shown. Similarly, the left articulation arm 13506 includes aleft articulation link 13512 and a left articulation bar 13514. Asshown, the left and right articulation arms cross and are connected tothe end effector via hinges next to the channel 13520. Pulling orpushing forces of the left and right articulation arms can cause the endeffector to articulate about the articulation pivots 13518. Theoff-center pivot link 13516 helps to stabilize the end effector as itarticulates, due to the off-center pivot link 13516 being stablypositioned into the shaft where the articulation arms reside, which isnot shown here for illustration purposes. The anvil 13502 is coupled tothe articulation joints via the anvil retainer 13522.

Referring to FIGS. 32-34, examples are shown of how movements of thearticulation arms cause the end effector to articulate, according tosome aspects. In FIG. 32, the anvil 13502 is in a neutral or straightposition relative to the articulation arms 13504 and 13506. In FIG. 33,the left articulation arm 13506 is moved up along direction B, whilesimultaneously the right articulation arm 13504 is moved down alongdirection C. Because the hinges of the articulation arms that connect tothe end effector are positioned on opposite sides of the articulationpivot 13518, these described motions cause the anvil 13502 to articulatein the counterclockwise direction A, as shown. This is consistent whennoticing the fact that the hinge of the left articulation arm 13506 isto the right of the pivot 13518, and therefore an upward movement indirection B is consistent with causing a counterclockwise motion.Similarly, because the hinge connecting the right articulation arm 13504is positioned to the left of the pivot 13518, a downward movement indirection C is consistent with causing a counterclockwise motion. Incontrast, as shown in FIG. 34, reverse movements by the articulationarms cause the anvil 13502 to move in the reverse, i.e., clockwise,direction. That is, a movement by the right articulation arm 13504 inthe upward direction B, and any simultaneous movement by the leftarticulation arm 13506 in the downward direction C, create a clockwisemotion of the anvil 13502 about the pivot 13518.

Referring to FIG. 35, according to some aspects, the pivot moment of theend effector is actually off from the centerline of the shaft structure.Shown here is the centerline 13528 of the shaft 13524, which representsthe point equidistant to opposite sides of the channel retainer 13526.The left and right articulation bars 13514 and 13510 are positionedwithin the channel retainer 13526 at spacing equidistant to thecenterline 13528. However, the articulation pivot 13518 is positionedslightly off-center, such as at a distance 13530 from the centerline13528. This in turn has the left articulation link 13512 positionedfurther away from the centerline 13528 in order to connect to thechannel 13520, compared to where the right articulation link 13508 isconnected to the channel 13520. The asymmetry of this design may haveseveral purposes. For example, the asymmetric design may create a morestable configuration when the articulation arms are oriented one on topof the other, e.g., the right articulation bar 13510 is above the leftarticulation bar 13514, as opposed to the shaft being rotated 90° suchthat the articulation arms are side-by-side to one another. The effectsof gravity create a need for greater stability over the top of the endeffector, suggesting an imbalance of forces needed to be applied to thearticulation arms. Second, the asymmetric design also creates a controlalgorithm with asymmetric properties. This creates a set of forcedratios between the two articulation arms that is unique at every point,in that the ratio of forces between the two articulation arms is alwaysgoing to be different. This design may help to diagnose problems anddebug issues between the interplay of the two articulation arms becauseit is known that the force ratio profile is unique at every point.

Referring to FIG. 36, illustration 13600 shows an example graphrepresenting an amount of force applied by both of the articulation armsas a function of a degree of articulation of the head from a horizontalcenterline, according to some aspects. As shown, the graph 13600 showsforce as the Y axis 13602, and a degree of articulation from ahorizontal centerline represents the X axis 13604. A maximum value 13606represents the maximum amount of force that the motors may apply to thearticulation arms. In this example, the curve 13608 represents an amountof force that should be applied to the left articulation arm 13506 as afunction of the desired articulation angle according to the X axis13604, and the curve 13610 represents an amount of force that should beapplied to the right articulation arm 13504 as a function of the samedesired articulation angle. In this example, the maximum range ofarticulation is +/−60° from the centerline.

In some aspects, causing articulation of the head/end effector involvesapplying forces to both of the articulation arms in an antagonisticrelationship. For example, each motor coupled to the articulation armsmay exert pulling forces on both of the articulation arms at the sametime. The ratio of the amount of pulling force between the twoarticulation arms may determine the angle at which the head/end effectorarticulates. This ratio of forces may be mapped or represented by thegraph 13600.

For example, in order to cause the head/end effector to articulate 45°from the centerline, a pulling force in the magnitude of length E shouldbe applied to the right articulation arm, according to the curve 13610.Simultaneously, a pulling force in the magnitude of length F should beapplied to the left articulation arm, according to the curve 13608. Ingeneral, the ratio between the magnitudes E and F may dictate whatarticulation angle is achieved, rather than the absolute magnitude ofthe forces themselves.

As another example, because the articulation pivot 13518 is locatedoff-center, the amount of counterbalancing or antagonistic forcesrequired to stabilize the head/end effector at an even 0° is not equalbetween the two articulation arms. This is exemplified by the forces E′and F′, which are different amounts of force applied to the twoarticulation arms at the 0° point in the graph 13600.

Referring to FIG. 37, shown is an example of how antagonistic forces maybe applied to the two articulation arms in order to cause the head/endeffector to articulate 60° from the centerline, according to someaspects. Here, a motor coupled to the right articulation arm 13504 mayapply a pulling force substantially greater than a pulling force appliedby a second motor to the left articulation arm 13506. The exact ratio offorces between the two articulation arms may be determined by theexample control algorithm graph 13600 in FIG. 36, according to theamounts of forces illustrated at the 60° line in the graph. The largeramount of pulling force applied to the right articulation arm 13504 incomparison to the left articulation arm 13506 results in the rightarticulation arm 13504 being pulled to the right in FIG. 37.Accordingly, this ratio of forces results in the left articulation arm13506 moving to the left or being pushed toward the head/end effector.However, because there is still some amount of pulling force beingapplied to the left articulation arm 13506, the antagonistic forceseffectively balance out or equilibrate at a point such that the head/endeffector articulates 60° from the centerline, as shown.

Referring to FIG. 38, shown is another example of how forces may beapplied to the two articulation arms in order to cause the head/endeffector to articulate 30° from the centerline, according to someaspects. Here, the motor coupled to the right articulation arm 13504 mayapply a pulling force greater than the pulling force applied to the leftarticulation arm 13506 by the second motor. In this case, the differencein the forces is not as substantial as the ones described in FIG. 37. Asan example, the exact ratio of forces between the two articulation armsmay be determined by the example control algorithm graph 13600 in FIG.36, according to the amount of forces illustrated at the 30° point inthe graph. It can be seen therefore that the ratio of the two forces issmaller, meaning the smaller, countervailing force applied to the leftarticulation arm 13506 is closer in magnitude to the prevailing forceapplied to the right articulation arm 13504. Starting from the positionof articulation in the illustration of FIG. 37, the change in forcesapplied to the two articulation arms in FIG. 38 results in an effectiveforce F_(E) 13706 applied to the head/end effector in FIG. 38. Thearrows 13702 and 13704 represent the changes in force applied to theirrespective articulation arms relative to the forces illustrated inprevious FIG. 37.

Referring to FIG. 39, shown is a third example of how forces may beapplied to the two articulation arms in order to cause the head/endeffector to articulate back to the center or neutral position, accordingto some aspects. Here, the motor coupled to the right articulation arm13504 may apply a pulling force less than a pulling force applied to theleft articulation arm 13506 by the second motor. As shown in the graph13600 of FIG. 36, the antagonistic pulling force of the leftarticulation arm 13506 is actually greater then the force applied to theright articulation arm 13504 at the 0° point. This makes sense whenconsidering that the articulation pivot 13518 is off-center and closerto the hinge of the left articulation arm 13506. This requires the leftarticulation arm 13506 to deliver more torque relative to the rightarticulation arm 13504 in order to balance the forces. In this example,the change in the amount of forces applied to both of the articulationarms compared to FIG. 38 results in an effective force F_(E) 13806 beingapplied to the center of mass of the head/end effector.

Referring to FIG. 40, a logic flow diagram depicting a process 13900illustrates an example methodology for causing articulation of an endeffector of a robotic surgical system based on controlling twoindependent articulation arms, according to some aspects. As shown inFIG. 30, the control circuit 2510 may be configured to command motorcontrol 2508 d and motor control 2508 e. These may be coupled torespective motors 2504 d and 2504 e. These motors may ultimatelyrespectively create a pulling or pushing force applied to thearticulation arms 13504 and 13506. The independent nature of the twomotors, while ultimately being used to control the articulation of asingle end effector, allows for a clean design that is easier to programin a precise manner and also diagnose for problems and replacementparts.

The control circuit, e.g., control circuit 2510, may be configured tocause 13902 the first articulation motor, e.g., motor 2504 d, to applyfirst force to the first articulation arm, e.g., articulation arm 2542 aor either of articulation arms 13504 and 13506. In some aspects, thefirst force may be a pulling force configured to draw the firstarticulation arm proximally toward the motor, while in other cases theforce may be a pushing force in the opposite direction relative to theend effector.

The control circuit may be configured to cause 13904 a secondarticulation motor, e.g., motor 2504 e, to apply a second force to asecond articulation arm, e.g., articulation arm 2542 b or the other ofarticulation arms 13504 and 13506. The second force applied isantagonistic to the first force, meaning the second force results in acounterbalancing or countervailing force in the opposite direction ofthe first force. As shown in the previous figures, this antagonisticforce may be a pulling force that causes a torque to be applied in theopposite direction about the articulation pivot of the end effector. Inother aspects, if the first force is a pushing force, then the secondforce may also be a pushing force but applied in an opposite directionrelative to the end effector.

The end effector that is coupled to the first and second articulationarms articulates 13906 about a pivot, where the degree of articulationis based on a ratio of the first and second forces. If the pivot aboutwhich the end effector articulates is positioned in between the hingesthat link the end effector to the two articulation arms, then theantagonistic second force should be the same type of force as the firstforce, e.g., both are pulling forces, or both are pushing forces. On theother hand, if both of the hinges connecting the two articulation armsto the end effector are located on the same side of the articulationpivot, then the antagonistic second force should be of the opposite typeof force as the first force, e.g., one is a pulling force and the otheris a pushing force. As shown in the previous examples, the articulationpivot may be located off-center from the centerline, allowing for aunique ratio of forces at all articulation angles.

The functions or processes 13900 described herein may be executed by anyof the processing circuits described herein, such as the control circuit961 (FIG. 22), 800 (FIG. 23), 810 (FIG. 24), 820 (FIG. 25), 4420 (FIG.26), and/or control circuit 2510 (FIG. 30). Aspects of the motorizedsurgical instrument may be practiced without the specific detailsdisclosed herein. Some aspects have been shown as block diagrams ratherthan detail.

Parts of this disclosure may be presented in terms of instructions thatoperate on data stored in a computer memory. An algorithm refers to aself-consistent sequence of steps leading to a desired result, where a“step” refers to a manipulation of physical quantities which may takethe form of electrical or magnetic signals capable of being stored,transferred, combined, compared, and otherwise manipulated. Thesesignals may be referred to as bits, values, elements, symbols,characters, terms, numbers. These and similar terms may be associatedwith the appropriate physical quantities and are merely convenientlabels applied to these quantities.

Generally, aspects described herein which can be implemented,individually and/or collectively, by a wide range of hardware, software,firmware, or any combination thereof can be viewed as being composed ofvarious types of “electrical circuitry.” Consequently, “electricalcircuitry” includes electrical circuitry having at least one discreteelectrical circuit, electrical circuitry having at least one integratedcircuit, electrical circuitry having at least one application specificintegrated circuit, electrical circuitry forming a general purposecomputing device configured by a computer program (e.g., a generalpurpose computer or processor configured by a computer program which atleast partially carries out processes and/or devices described herein,electrical circuitry forming a memory device (e.g., forms of randomaccess memory), and/or electrical circuitry forming a communicationsdevice (e.g., a modem, communications switch, or optical-electricalequipment). These aspects may be implemented in analog or digital form,or combinations thereof.

The foregoing description has set forth aspects of devices and/orprocesses via the use of block diagrams, flowcharts, and/or examples,which may contain one or more functions and/or operation. Each functionand/or operation within such block diagrams, flowcharts, or examples canbe implemented, individually and/or collectively, by a wide range ofhardware, software, firmware, or virtually any combination thereof. Inone aspect, several portions of the subject matter described herein maybe implemented via Application Specific Integrated Circuits (ASICs),Field Programmable Gate Arrays (FPGAs), digital signal processors(DSPs), Programmable Logic Devices (PLDs), circuits, registers and/orsoftware components, e.g., programs, subroutines, logic and/orcombinations of hardware and software components. logic gates, or otherintegrated formats. Some aspects disclosed herein, in whole or in part,can be equivalently implemented in integrated circuits, as one or morecomputer programs running on one or more computers (e.g., as one or moreprograms running on one or more computer systems), as one or moreprograms running on one or more processors (e.g., as one or moreprograms running on one or more microprocessors), as firmware, or asvirtually any combination thereof, and that designing the circuitryand/or writing the code for the software and or firmware would be wellwithin the skill of one of skill in the art in light of this disclosure.

The mechanisms of the disclosed subject matter are capable of beingdistributed as a program product in a variety of forms, and that anillustrative aspect of the subject matter described herein appliesregardless of the particular type of signal bearing medium used toactually carry out the distribution. Examples of a signal bearing mediuminclude the following: a recordable type medium such as a floppy disk, ahard disk drive, a Compact Disc (CD), a Digital Video Disk (DVD), adigital tape, a computer memory, etc.; and a transmission type mediumsuch as a digital and/or an analog communication medium (e.g., a fiberoptic cable, a waveguide, a wired communications link, a wirelesscommunication link (e.g., transmitter, receiver, transmission logic,reception logic, etc.).

The foregoing description of these aspects has been presented forpurposes of illustration and description. It is not intended to beexhaustive or limiting to the precise form disclosed. Modifications orvariations are possible in light of the above teachings. These aspectswere chosen and described in order to illustrate principles andpractical application to thereby enable one of ordinary skill in the artto utilize the aspects and with modifications as are suited to theparticular use contemplated. It is intended that the claims submittedherewith define the overall scope.

Various aspects of the subject matter described herein are set out inthe following examples:

Example 1

A system for a robotic surgical instrument, the system comprising: acontrol circuit; a first motor and a second motor, both communicativelycoupled to the control circuit; a first articulation arm communicativelycoupled to the first motor; a second articulation arm communicativelycoupled to the second motor; and an end effector coupled to the firstarticulation arm via a first hinge and the second articulation arm via asecond hinge; wherein: the control circuit is configured to cause thefirst motor to apply a first force to the first articulation arm; thecontrol circuit is configured to cause the second motor to apply asecond force to the second articulation arm, wherein the second force isantagonistic to the first force such that the first and second forcesapply counteracting forces at the end effector; and the first and secondforces cause the end effector to articulate via the first and secondhinges.

Example 2

The system of Example 1, wherein the end effector is configured toarticulate to a prescribed angle based on a ratio of magnitudes betweenthe first force and the second force.

Example 3

The system of one or more of Example 1 through Example 2, furthercomprising an articulation pivot coupled to the end effector, whereinthe end effector is further configured to articulate about thearticulation pivot.

Example 4

The system of Example 3, wherein the articulation pivot is positionedoff of a center axis running longitudinally in between and equidistantfrom at least a portion of the first and second articulation arms.

Example 5

The system of one or more of Example 3 through Example 4, furthercomprising a shaft encapsulating the first and second articulation arms.

Example 6

The system of Example 5, further comprising a pivot link coupled to thearticulation pivot and stably positioned within the shaft, wherein thepivot link is configured to stabilize the end effector while the endeffector articulates about the articulation pivot.

Example 7

The system of Example 6, wherein the pivot link and the articulationpivot are positioned off of a center axis running longitudinally inbetween and equidistant from at least a portion of the first and secondarticulation arms.

Example 8

The system of Example 7, wherein the first force is greater than thesecond force when the end effector is articulated to a zero degree anglefrom a center position.

Example 9

The system of one or more of Example 1 through Example 8, wherein thecontrol circuit is configured to operate the first motor independent ofthe second motor.

Example 10

The system of one or more of Example 1 through Example 9, wherein thefirst and second forces are pulling forces applied to the first andsecond articulation arms, respectively.

Example 11

The system of one or more of Example 1 through Example 10, wherein thefirst and second forces are pushing forces applied to the first andsecond articulation arms, respectively.

Example 12

A method of a robotic surgical instrument comprising a control circuit,a first motor, a second motor, a first articulation arm, a secondarticulation arm, and an end effector, the method comprising:instructing, by the control circuit, the first motor to apply a firstforce to the first articulation arm; instructing, by the controlcircuit, the second motor to apply a second force to the secondarticulation arm, wherein the second force is antagonistic to the firstforce such that the first and second forces apply counteracting forcesat the end effector; and causing the end effector to articulate viafirst and second hinges based on the first and second forces applied tothe first and second articulation arms, respectively.

Example 13

The method of Example 12, further comprising causing the end effector toarticulate to a prescribed angle based on a ratio of magnitudes betweenthe first force and the second force.

Example 14

The method of one or more of Example 12 through Example 13, wherein therobotic surgical instrument further comprises an articulation pivotcoupled to the end effector, wherein the end effector furtherarticulates about the articulation pivot.

Example 15

The method of Example 14, wherein the articulation pivot is positionedoff of a center axis running longitudinally in between and equidistantfrom at least a portion of the first and second articulation arms.

Example 16

The method of one or more of Example 14 through Example 15, wherein therobotic surgical instrument further comprises a shaft encapsulating thefirst and second articulation arms.

Example 17

The method of one or more of Example 15 through Example 16, wherein thefirst force is greater than the second force when the end effector isarticulated to a zero degree angle from a center position.

Example 18

The method of one or more of Example 12 through Example 17, whereinapplying the first force to the first motor is independent of applyingthe second force to the second motor.

Example 19

The method of one or more of Example 1 through Example 18, wherein thefirst and second forces are pulling forces applied to the first andsecond articulation arms, respectively.

Example 20

The method of one or more of Example 12 through Example 19, wherein thefirst and second forces are pushing forces applied to the first andsecond articulation arms, respectively.

The invention claimed is:
 1. A system for a robotic surgical instrument,the system comprising: a control circuit; a first motor and a secondmotor, both communicatively coupled to the control circuit; a firstarticulation arm communicatively coupled to the first motor; a secondarticulation arm communicatively coupled to the second motor; and an endeffector coupled to the first articulation arm via a first hinge and thesecond articulation arm via a second hinge; wherein: the control circuitis configured to cause the first motor to apply a first force to thefirst articulation arm; the control circuit is configured to cause thesecond motor to apply a second force to the second articulation arm,wherein the second force is antagonistic to the first force such thatthe first and second forces apply counteracting forces at the endeffector; the first and second forces cause the end effector toarticulate via the first and second hinges; and the end effector isconfigured to articulate to a prescribed angle based on a ratio ofmagnitudes between the first force and the second force.
 2. The systemof claim 1, further comprising an articulation pivot coupled to the endeffector, wherein the end effector is further configured to articulateabout the articulation pivot.
 3. The system of claim 2, wherein thearticulation pivot is positioned off of a center axis runninglongitudinally in between and equidistant from at least a portion of thefirst and second articulation arms.
 4. The system of claim 2, furthercomprising a shaft encapsulating the first and second articulation arms.5. The system of claim 4, further comprising a pivot link coupled to thearticulation pivot and stably positioned within the shaft, wherein thepivot link is configured to stabilize the end effector while the endeffector articulates about the articulation pivot.
 6. The system ofclaim 5, wherein the pivot link and the articulation pivot arepositioned off of a center axis running longitudinally in between andequidistant from at least a portion of the first and second articulationarms.
 7. The system of claim 6, wherein the first force is greater thanthe second force when the end effector is articulated to a zero degreeangle from a center position.
 8. The system of claim 1, wherein thecontrol circuit is configured to operate the first motor independent ofthe second motor.
 9. The system of claim 1, wherein the first and secondforces are pulling forces applied to the first and second articulationarms, respectively.
 10. The system of claim 1, wherein the first andsecond forces are pushing forces applied to the first and secondarticulation arms, respectively.
 11. A method of a robotic surgicalinstrument comprising a control circuit, a first motor, a second motor,a first articulation arm, a second articulation arm, and an endeffector, the method comprising: instructing, by the control circuit,the first motor to apply a first force to the first articulation arm;instructing, by the control circuit, the second motor to apply a secondforce to the second articulation arm, wherein the second force isantagonistic to the first force such that the first and second forcesapply counteracting forces at the end effector; and causing the endeffector to articulate to a prescribed angle via first and secondhinges, based on the first and second forces applied to the first andsecond articulation arms, respectively, and based on a ratio ofmagnitudes between the first force and the second force.
 12. The methodof claim 11, wherein the robotic surgical instrument further comprisesan articulation pivot coupled to the end effector, wherein the endeffector further articulates about the articulation pivot.
 13. Themethod of claim 12, wherein the articulation pivot is positioned off ofa center axis running longitudinally in between and equidistant from atleast a portion of the first and second articulation arms.
 14. Themethod of claim 12, wherein the robotic surgical instrument furthercomprises a shaft encapsulating the first and second articulation arms.15. The method of claim 13, wherein the first force is greater than thesecond force when the end effector is articulated to a zero degree anglefrom a center position.
 16. The method of claim 11, wherein applying thefirst force from the first motor is independent of applying the secondforce from the second motor.
 17. The method of claim 11, wherein thefirst and second forces are pulling forces applied to the first andsecond articulation arms, respectively.
 18. The method of claim 11,wherein the first and second forces are pushing forces applied to thefirst and second articulation arms, respectively.